diff --git a/res/values-ru/strings.xml b/res/values-ru/strings.xml
index 5f4b108b..e4d49319 100644
--- a/res/values-ru/strings.xml
+++ b/res/values-ru/strings.xml
@@ -85,4 +85,11 @@
 	<string name="c_calc_theme_summary">Устанавливает тему оформления приложения</string>
 	<string name="c_clear_history">Очистить историю</string>
 	<string name="c_simplify_instead_of_numeric">Следующие константы не определены: {0}!</string>
+
+	<string name="p_grouping_separator_no">Не использовать разделитель разрядов</string>
+	<string name="p_grouping_separator_apostrophe">Апостроф (\')</string>
+	<string name="p_grouping_separator_space">Пробел ( )</string>
+	<string name="c_calc_grouping_separator">Разделитель разрядов</string>
+	<string name="c_calc_grouping_separator_summary">Устанавливает разделитель разрядов числа</string>
+
 </resources>
diff --git a/res/values/arrays.xml b/res/values/arrays.xml
index 5c57dc96..eff788ab 100644
--- a/res/values/arrays.xml
+++ b/res/values/arrays.xml
@@ -15,4 +15,16 @@
 		<item>violet_theme</item>
 		<item>light_blue_theme</item>
 	</string-array>
+
+	<string-array name="p_grouping_separator_names">
+		<item>@string/p_grouping_separator_no</item>
+		<item>@string/p_grouping_separator_apostrophe</item>
+		<item>@string/p_grouping_separator_space</item>
+	</string-array>
+	<string-array name="p_grouping_separator_values">
+		<item>""</item>
+		<item>\'</item>
+		<item> </item>
+	</string-array>
+
 </resources>
\ No newline at end of file
diff --git a/res/values/default_values.xml b/res/values/default_values.xml
index 5b8b8f63..783249c7 100644
--- a/res/values/default_values.xml
+++ b/res/values/default_values.xml
@@ -24,4 +24,7 @@
 	<string name="p_calc_theme_key">org.solovyev.android.calculator.CalculatorActivity_calc_theme</string>
 	<string name="p_calc_theme">default_theme</string>
 
+	<string name="p_calc_grouping_separator_key">org.solovyev.android.calculator.CalculatorActivity_calc_grouping_separator</string>
+	<string name="p_calc_grouping_separator"> </string>
+
 </resources>
\ No newline at end of file
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 6e0d68ac..7ca826b0 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -85,4 +85,10 @@
 	<string name="c_calc_theme_summary">Sets the theme for calculator</string>
 	<string name="c_clear_history">Clear history</string>
 	<string name="c_simplify_instead_of_numeric">Next constants are undefined: {0}!</string>
+
+	<string name="p_grouping_separator_no">No grouping separator</string>
+	<string name="p_grouping_separator_apostrophe">Apostrophe (\')</string>
+	<string name="p_grouping_separator_space">Space ( )</string>
+	<string name="c_calc_grouping_separator">Grouping separator</string>
+	<string name="c_calc_grouping_separator_summary">Sets grouping separator</string>
 </resources>
diff --git a/res/xml/main_preferences.xml b/res/xml/main_preferences.xml
index 7c266342..b0fa9f55 100644
--- a/res/xml/main_preferences.xml
+++ b/res/xml/main_preferences.xml
@@ -17,13 +17,17 @@
 				a:title="@string/c_calc_color_display_title"
 				a:defaultValue="true"/>
 
+		<ListPreference a:key="@string/p_calc_grouping_separator_key"
+						a:title="@string/c_calc_grouping_separator"
+						a:entries="@array/p_grouping_separator_names"
+						a:summary="@string/c_calc_grouping_separator_summary"
+						a:entryValues="@array/p_grouping_separator_values"/>
+
 		<ListPreference a:key="@string/p_calc_theme_key"
 						a:title="@string/c_calc_theme"
 						a:entries="@array/p_theme_names"
 						a:summary="@string/c_calc_theme_summary"
-						a:entryValues="@array/p_theme_values"
-						a:persistent="true"
-						a:shouldDisableView="false"/>
+						a:entryValues="@array/p_theme_values"/>
 
 
 		<!--		<org.solovyev.android.view.prefs.FloatRangeSeekBarPreference
diff --git a/src/main/java/org/solovyev/android/calculator/CalculatorDisplay.java b/src/main/java/org/solovyev/android/calculator/CalculatorDisplay.java
index bf01d675..3fa78fad 100644
--- a/src/main/java/org/solovyev/android/calculator/CalculatorDisplay.java
+++ b/src/main/java/org/solovyev/android/calculator/CalculatorDisplay.java
@@ -25,7 +25,7 @@ public class CalculatorDisplay extends TextView {
 	private boolean valid = true;
 
 	@NotNull
-	private final static TextProcessor<String> textHighlighter = new TextHighlighter(Color.WHITE);
+	private final static TextProcessor<TextHighlighter.Result> textHighlighter = new TextHighlighter(Color.WHITE);
 
 	public CalculatorDisplay(Context context) {
 		super(context);
@@ -61,7 +61,8 @@ public class CalculatorDisplay extends TextView {
 			Log.d(this.getClass().getName(), text);
 
 			try {
-				text = textHighlighter.process(text);
+				TextHighlighter.Result result = textHighlighter.process(text);
+				text = result.toString();
 			} catch (ParseException e) {
 				Log.e(this.getClass().getName(), e.getMessage(), e);
 			}
diff --git a/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java b/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java
index 9857d542..661cba37 100644
--- a/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java
+++ b/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java
@@ -26,7 +26,7 @@ public class CalculatorEditor extends EditText {
 	private boolean highlightText = true;
 
 	@NotNull
-	private final static TextProcessor<String> textHighlighter = new TextHighlighter(Color.WHITE);
+	private final static TextProcessor<TextHighlighter.Result> textHighlighter = new TextHighlighter(Color.WHITE);
 
 	public CalculatorEditor(Context context) {
 		super(context);
@@ -69,7 +69,10 @@ public class CalculatorEditor extends EditText {
 			Log.d(this.getClass().getName(), text);
 
 			try {
-				text = textHighlighter.process(text);
+				final TextHighlighter.Result result = textHighlighter.process(text);
+				selectionStart += result.getOffset();
+				selectionEnd += result.getOffset();
+				text = result.toString();
 			} catch (ParseException e) {
 				Log.e(this.getClass().getName(), e.getMessage(), e);
 			}
diff --git a/src/main/java/org/solovyev/android/calculator/TextHighlighter.java b/src/main/java/org/solovyev/android/calculator/TextHighlighter.java
index 127c991f..f99d7182 100644
--- a/src/main/java/org/solovyev/android/calculator/TextHighlighter.java
+++ b/src/main/java/org/solovyev/android/calculator/TextHighlighter.java
@@ -11,13 +11,51 @@ import org.solovyev.android.calculator.math.MathType;
 import org.solovyev.android.calculator.model.NumberBuilder;
 import org.solovyev.android.calculator.model.ParseException;
 import org.solovyev.android.calculator.model.TextProcessor;
+import org.solovyev.common.utils.MutableObject;
 
 /**
  * User: serso
  * Date: 10/12/11
  * Time: 9:47 PM
  */
-public class TextHighlighter implements TextProcessor<String> {
+public class TextHighlighter implements TextProcessor<TextHighlighter.Result> {
+
+	public static class Result implements CharSequence {
+
+		@NotNull
+		private final String string;
+
+		private final int offset;
+
+		public Result(@NotNull String string, int offset) {
+			this.string = string;
+			this.offset = offset;
+		}
+
+		@Override
+		public int length() {
+			return string.length();
+		}
+
+		@Override
+		public char charAt(int i) {
+			return string.charAt(i);
+		}
+
+		@Override
+		public CharSequence subSequence(int i, int i1) {
+			return string.subSequence(i, i1);
+		}
+
+		@Override
+		public String toString() {
+			return string;
+		}
+
+		public int getOffset() {
+			return offset;
+		}
+	}
 
 	private final int color;
 	private final int colorRed;
@@ -36,7 +74,7 @@ public class TextHighlighter implements TextProcessor<String> {
 
 	@NotNull
 	@Override
-	public String process(@NotNull String text) throws ParseException {
+	public Result process(@NotNull String text) throws ParseException {
 		final String result;
 
 		int maxNumberOfOpenGroupSymbols = 0;
@@ -44,11 +82,15 @@ public class TextHighlighter implements TextProcessor<String> {
 
 		final StringBuilder text1 = new StringBuilder();
 
+		int numberOffset = 0;
+
 		final NumberBuilder numberBuilder = new NumberBuilder();
 		for (int i = 0; i < text.length(); i++) {
-			final MathType.Result mathType = MathType.getType(text, i);
+			MathType.Result mathType = MathType.getType(text, i);
 
-		    numberBuilder.process(text1, mathType);
+			final MutableObject<Integer> localNumberOffset  = new MutableObject<Integer>(0);
+		    numberBuilder.process(text1, mathType, localNumberOffset);
+			numberOffset += localNumberOffset.getObject();
 
 			switch (mathType.getMathType()) {
 				case open_group_symbol:
@@ -71,7 +113,9 @@ public class TextHighlighter implements TextProcessor<String> {
 			}
 		}
 
-		numberBuilder.process(text1);
+		final MutableObject<Integer> localNumberOffset  = new MutableObject<Integer>(0);
+		numberBuilder.process(text1, localNumberOffset);
+		numberOffset += localNumberOffset.getObject();
 
 		if (maxNumberOfOpenGroupSymbols > 0) {
 
@@ -90,7 +134,7 @@ public class TextHighlighter implements TextProcessor<String> {
 			result = text1.toString();
 		}
 
-		return result;
+		return new Result(result, numberOffset);
 	}
 
 	private int processHighlightedText(@NotNull StringBuilder result, int i, @NotNull String functionName, @NotNull String tag) {
diff --git a/src/main/java/org/solovyev/android/calculator/math/MathType.java b/src/main/java/org/solovyev/android/calculator/math/MathType.java
index 9f44cd4e..3437982a 100644
--- a/src/main/java/org/solovyev/android/calculator/math/MathType.java
+++ b/src/main/java/org/solovyev/android/calculator/math/MathType.java
@@ -198,13 +198,21 @@ public enum MathType {
 	public int processToJscl(@NotNull StringBuilder result, int i, @NotNull String match) {
 		final String substitute = getSubstituteToJscl(match);
 		result.append(substitute == null ? match : substitute);
-		return i + match.length() - 1;
+		if (match.length() > 1) {
+			return i + match.length() - 1;
+		} else {
+			return i;
+		}
 	}
 
 	public int processFromJscl(@NotNull StringBuilder result, int i, @NotNull String match) {
 		final String substitute = getSubstituteFromJscl(match);
 		result.append(substitute == null ? match : substitute);
-		return i + match.length() - 1;
+		if (match.length() > 1) {
+			return i + match.length() - 1;
+		} else {
+			return i;
+		}
 	}
 
 	@Nullable
diff --git a/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java b/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java
index 3082e3d7..88589b7c 100644
--- a/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java
+++ b/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java
@@ -20,6 +20,7 @@ import org.solovyev.common.msg.MessageType;
 import org.solovyev.common.utils.CollectionsUtils;
 import org.solovyev.common.utils.Formatter;
 import org.solovyev.common.utils.MutableObject;
+import org.solovyev.common.utils.StringUtils;
 
 import java.math.BigDecimal;
 import java.text.DecimalFormat;
@@ -40,6 +41,9 @@ public enum CalculatorEngine {
 
 	instance;
 
+	private static final String GROUPING_SEPARATOR_P_KEY = "org.solovyev.android.calculator.CalculatorActivity_calc_grouping_separator";
+	private static final String GROUPING_SEPARATOR_DEFAULT = " ";
+
 	private static final String RESULT_PRECISION_P_KEY = "org.solovyev.android.calculator.CalculatorModel_result_precision";
 	private static final String RESULT_PRECISION_DEFAULT = "5";
 
@@ -62,6 +66,12 @@ public enum CalculatorEngine {
 
 	@NotNull
 	private DecimalFormatSymbols decimalGroupSymbols = new DecimalFormatSymbols(Locale.getDefault());
+	{
+		decimalGroupSymbols.setDecimalSeparator('.');
+		decimalGroupSymbols.setGroupingSeparator(GROUPING_SEPARATOR_DEFAULT.charAt(0));
+	}
+
+	private boolean useGroupingSeparator = true;
 
 	@NotNull
 	private ThreadKiller threadKiller = new AndroidThreadKiller();
@@ -71,7 +81,7 @@ public enum CalculatorEngine {
 		if (!value.isInfinite() && !value.isNaN()) {
 			final DecimalFormat df = new DecimalFormat();
 			df.setDecimalFormatSymbols(decimalGroupSymbols);
-			df.setGroupingUsed(true);
+			df.setGroupingUsed(useGroupingSeparator);
 			df.setMaximumFractionDigits(instance.getPrecision());
 			return df.format(new BigDecimal(value).setScale(instance.getPrecision(), BigDecimal.ROUND_HALF_UP).doubleValue());
 		} else {
@@ -79,11 +89,6 @@ public enum CalculatorEngine {
 		}
 	}
 
-	{
-		decimalGroupSymbols.setDecimalSeparator('.');
-		decimalGroupSymbols.setGroupingSeparator(' ');
-	}
-
 	public String evaluate(@NotNull JsclOperation operation,
 						   @NotNull String expression) throws EvalError, ParseException {
 		return evaluate(operation, expression, null);
@@ -201,6 +206,14 @@ public enum CalculatorEngine {
 				final NumberMapper<Integer> integerNumberMapper = new NumberMapper<Integer>(Integer.class);
 				//noinspection ConstantConditions
 				this.setPrecision(integerNumberMapper.parseValue(preferences.getString(RESULT_PRECISION_P_KEY, RESULT_PRECISION_DEFAULT)));
+
+				final String groupingSeparator = preferences.getString(GROUPING_SEPARATOR_P_KEY, GROUPING_SEPARATOR_DEFAULT);
+				if (StringUtils.isEmpty(groupingSeparator)) {
+					this.useGroupingSeparator = false;
+				} else {
+					this.useGroupingSeparator = true;
+					this.decimalGroupSymbols.setGroupingSeparator(groupingSeparator.charAt(0));
+				}
 			}
 
 			varsRegister.init(context, preferences);
@@ -218,7 +231,8 @@ public enum CalculatorEngine {
 		}
 	}
 
-	public void setDecimalGroupSymbols(@NotNull DecimalFormatSymbols decimalGroupSymbols) {
+	//for tests only
+	void setDecimalGroupSymbols(@NotNull DecimalFormatSymbols decimalGroupSymbols) {
 		synchronized (lock) {
 			this.decimalGroupSymbols = decimalGroupSymbols;
 		}
diff --git a/src/main/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessor.java b/src/main/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessor.java
index 4d7c4b3d..5daf6e38 100644
--- a/src/main/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessor.java
+++ b/src/main/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessor.java
@@ -14,7 +14,6 @@ import java.util.List;
  */
 public class FromJsclSimplifyTextProcessor implements TextProcessor<String> {
 
-
 	@NotNull
 	@Override
 	public String process(@NotNull String s) throws ParseException {
@@ -27,14 +26,14 @@ public class FromJsclSimplifyTextProcessor implements TextProcessor<String> {
 				continue;
 			}
 
-			final MathType.Result mathTypeResult = MathType.getType(s, i);
+			MathType.Result mathTypeResult = MathType.getType(s, i);
 
-			numberBuilder.process(sb, mathTypeResult);
+			numberBuilder.process(sb, mathTypeResult, null);
 
 			i = mathTypeResult.processFromJscl(sb, i);
 		}
 
-		numberBuilder.process(sb);
+		numberBuilder.process(sb, null);
 
 		return removeMultiplicationSigns(sb.toString());
 	}
diff --git a/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java b/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java
index 04bdc81a..24e7d82c 100644
--- a/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java
+++ b/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java
@@ -11,6 +11,7 @@ import org.jetbrains.annotations.Nullable;
 import org.solovyev.android.calculator.math.MathType;
 import org.solovyev.common.utils.CollectionsUtils;
 import org.solovyev.common.utils.Finder;
+import org.solovyev.common.utils.MutableObject;
 
 /**
 * User: serso
@@ -24,21 +25,28 @@ public class NumberBuilder {
 	@Nullable
 	private String number = null;
 
-	public void process(@NotNull StringBuilder sb, @NotNull MathType.Result mathTypeResult) {
+	@NotNull
+	public MathType.Result process(@NotNull StringBuilder sb, @NotNull MathType.Result mathTypeResult, @Nullable MutableObject<Integer> numberOffset) {
 		number = null;
+
+		final MathType.Result possibleResult;
 		if (mathTypeResult.getMathType() == MathType.digit || mathTypeResult.getMathType() == MathType.dot || mathTypeResult.getMathType() == MathType.power_10) {
 			if (numberBuilder == null) {
 				numberBuilder = new StringBuilder();
 			}
 			numberBuilder.append(mathTypeResult.getMatch());
 
-			replaceSystemVars(sb, number);
+			possibleResult = replaceSystemVars(sb, number, numberOffset);
 		} else {
-			process(sb);
+			possibleResult = process(sb, numberOffset);
 		}
+
+		return possibleResult == null ? mathTypeResult : possibleResult;
 	}
 
-	public void process(@NotNull StringBuilder sb) {
+
+	@Nullable
+	public MathType.Result process(@NotNull StringBuilder sb, @Nullable MutableObject<Integer> numberOffset) {
 		if (numberBuilder != null) {
 			try {
 				number = numberBuilder.toString();
@@ -52,12 +60,12 @@ public class NumberBuilder {
 			number = null;
 		}
 
-		replaceSystemVars(sb, number);
+		return replaceSystemVars(sb, number, numberOffset);
 	}
 
 	@Nullable
-	private MathType replaceSystemVars(StringBuilder sb, String number) {
-		MathType result = null;
+	private MathType.Result replaceSystemVars(StringBuilder sb, String number, @Nullable MutableObject<Integer> numberOffset) {
+		MathType.Result result = null;
 
 		if (number != null) {
 			final String finalNumber = number;
@@ -71,10 +79,14 @@ public class NumberBuilder {
 			if (var != null) {
 				sb.delete(sb.length() - number.length(), sb.length());
 				sb.append(var.getName());
-				result = MathType.constant;
+				result = new MathType.Result(MathType.constant, var.getName());
 			} else {
 				sb.delete(sb.length() - number.length(), sb.length());
-				sb.append(CalculatorEngine.instance.format(Double.valueOf(number)));
+				final String formattedNumber = CalculatorEngine.instance.format(Double.valueOf(number));
+				if ( numberOffset != null ) {
+					numberOffset.setObject(formattedNumber.length() - number.length());
+				}
+				sb.append(formattedNumber);
 			}
 		}
 
diff --git a/src/test/java/org/solovyev/android/calculator/TextHighlighterTest.java b/src/test/java/org/solovyev/android/calculator/TextHighlighterTest.java
index d5bdd31c..acc0e4d7 100644
--- a/src/test/java/org/solovyev/android/calculator/TextHighlighterTest.java
+++ b/src/test/java/org/solovyev/android/calculator/TextHighlighterTest.java
@@ -38,9 +38,9 @@ public class TextHighlighterTest {
 			}
 		}
 
-		Assert.assertEquals("<font color=\"#000000\"></font>)(((())())", textHighlighter.process(")(((())())"));
-		Assert.assertEquals(")", textHighlighter.process(")"));
-		Assert.assertEquals(")()(", textHighlighter.process(")()("));
-		Assert.assertEquals("1 000 000", textHighlighter.process("1000000"));
+		Assert.assertEquals("<font color=\"#000000\"></font>)(((())())", textHighlighter.process(")(((())())").toString());
+		Assert.assertEquals(")", textHighlighter.process(")").toString());
+		Assert.assertEquals(")()(", textHighlighter.process(")()(").toString());
+		Assert.assertEquals("1 000 000", textHighlighter.process("1000000").toString());
 	}
 }
diff --git a/src/test/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessorTest.java b/src/test/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessorTest.java
index e534d41d..3462e03d 100644
--- a/src/test/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessorTest.java
+++ b/src/test/java/org/solovyev/android/calculator/model/FromJsclSimplifyTextProcessorTest.java
@@ -22,6 +22,8 @@ public class FromJsclSimplifyTextProcessorTest {
 	public void testProcess() throws Exception {
 		FromJsclSimplifyTextProcessor tp = new FromJsclSimplifyTextProcessor();
 		Assert.assertEquals("(e)", tp.process("(2.718281828459045)"));
+		Assert.assertEquals("ee", tp.process("2.718281828459045*2.718281828459045"));
+		Assert.assertEquals("((e)(e))", tp.process("((2.718281828459045)*(2.718281828459045))"));
 		DecimalFormatSymbols decimalGroupSymbols = new DecimalFormatSymbols();
 		decimalGroupSymbols.setGroupingSeparator(' ');
 		CalculatorEngine.instance.setDecimalGroupSymbols(decimalGroupSymbols);
@@ -33,6 +35,7 @@ public class FromJsclSimplifyTextProcessorTest {
 
 		CalculatorEngine.instance.getVarsRegister().addVar(null, new Var.Builder("t2.718281828459045", "2"));
 		Assert.assertEquals("t2.718281828459045e", tp.process("t2.718281828459045*2.718281828459045"));
+		Assert.assertEquals("ee", tp.process("2.718281828459045*2.718281828459045"));
 		Assert.assertEquals("t×", tp.process("t*"));
 		Assert.assertEquals("×t", tp.process("*t"));
 		Assert.assertEquals("t×2", tp.process("t*2"));