diff --git a/src/Angular.js b/src/Angular.js
index 87bce33cca96..559c6362f97e 100644
--- a/src/Angular.js
+++ b/src/Angular.js
@@ -399,6 +399,10 @@ function toInt(str) {
   return parseInt(str, 10);
 }
 
+var isNumberNaN = Number.isNaN || function isNumberNaN(num) {
+  return num !== num;
+};
+
 
 function inherit(parent, extra) {
   return extend(Object.create(parent), extra);
@@ -1113,7 +1117,7 @@ function fromJson(json) {
 
 function timezoneToOffset(timezone, fallback) {
   var requestedTimezoneOffset = Date.parse('Jan 01, 1970 00:00:00 ' + timezone) / 60000;
-  return isNaN(requestedTimezoneOffset) ? fallback : requestedTimezoneOffset;
+  return isNumberNaN(requestedTimezoneOffset) ? fallback : requestedTimezoneOffset;
 }
 
 
diff --git a/src/ng/directive/input.js b/src/ng/directive/input.js
index e59ae067582d..e64bc3cfbc54 100644
--- a/src/ng/directive/input.js
+++ b/src/ng/directive/input.js
@@ -1259,7 +1259,7 @@ function numberInputType(scope, element, attr, ctrl, $sniffer, $browser) {
       if (isDefined(val) && !isNumber(val)) {
         val = parseFloat(val, 10);
       }
-      minVal = isNumber(val) && !isNaN(val) ? val : undefined;
+      minVal = !isNumberNaN(val) ? val : undefined;
       // TODO(matsko): implement validateLater to reduce number of validations
       ctrl.$validate();
     });
@@ -1275,7 +1275,7 @@ function numberInputType(scope, element, attr, ctrl, $sniffer, $browser) {
       if (isDefined(val) && !isNumber(val)) {
         val = parseFloat(val, 10);
       }
-      maxVal = isNumber(val) && !isNaN(val) ? val : undefined;
+      maxVal = !isNumberNaN(val) ? val : undefined;
       // TODO(matsko): implement validateLater to reduce number of validations
       ctrl.$validate();
     });
diff --git a/src/ng/directive/ngModel.js b/src/ng/directive/ngModel.js
index 6098cd08a829..f5d3baf50111 100644
--- a/src/ng/directive/ngModel.js
+++ b/src/ng/directive/ngModel.js
@@ -506,7 +506,7 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
    */
   this.$validate = function() {
     // ignore $validate before model is initialized
-    if (isNumber(ctrl.$modelValue) && isNaN(ctrl.$modelValue)) {
+    if (isNumberNaN(ctrl.$modelValue)) {
       return;
     }
 
@@ -676,7 +676,7 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
         }
       }
     }
-    if (isNumber(ctrl.$modelValue) && isNaN(ctrl.$modelValue)) {
+    if (isNumberNaN(ctrl.$modelValue)) {
       // ctrl.$modelValue has not been touched yet...
       ctrl.$modelValue = ngModelGet($scope);
     }
diff --git a/src/ng/directive/ngPluralize.js b/src/ng/directive/ngPluralize.js
index 8a1b11a959e3..ace473fb9fc4 100644
--- a/src/ng/directive/ngPluralize.js
+++ b/src/ng/directive/ngPluralize.js
@@ -207,7 +207,7 @@ var ngPluralizeDirective = ['$locale', '$interpolate', '$log', function($locale,
 
       scope.$watch(numberExp, function ngPluralizeWatchAction(newVal) {
         var count = parseFloat(newVal);
-        var countIsNaN = isNaN(count);
+        var countIsNaN = isNumberNaN(count);
 
         if (!countIsNaN && !(count in whens)) {
           // If an explicit number rule such as 1, 2, 3... is defined, just use it.
@@ -217,7 +217,7 @@ var ngPluralizeDirective = ['$locale', '$interpolate', '$log', function($locale,
 
         // If both `count` and `lastCount` are NaN, we don't need to re-register a watch.
         // In JS `NaN !== NaN`, so we have to exlicitly check.
-        if ((count !== lastCount) && !(countIsNaN && isNumber(lastCount) && isNaN(lastCount))) {
+        if ((count !== lastCount) && !(countIsNaN && isNumberNaN(lastCount))) {
           watchRemover();
           var whenExpFn = whensExpFns[count];
           if (isUndefined(whenExpFn)) {
diff --git a/src/ng/directive/validators.js b/src/ng/directive/validators.js
index ef7650f10ceb..f12afc18395e 100644
--- a/src/ng/directive/validators.js
+++ b/src/ng/directive/validators.js
@@ -61,7 +61,7 @@ var maxlengthDirective = function() {
       var maxlength = -1;
       attr.$observe('maxlength', function(value) {
         var intVal = toInt(value);
-        maxlength = isNaN(intVal) ? -1 : intVal;
+        maxlength = isNumberNaN(intVal) ? -1 : intVal;
         ctrl.$validate();
       });
       ctrl.$validators.maxlength = function(modelValue, viewValue) {
diff --git a/src/ng/filter/limitTo.js b/src/ng/filter/limitTo.js
index 02e227686ded..a6e94783fdbc 100644
--- a/src/ng/filter/limitTo.js
+++ b/src/ng/filter/limitTo.js
@@ -96,7 +96,7 @@ function limitToFilter() {
     } else {
       limit = toInt(limit);
     }
-    if (isNaN(limit)) return input;
+    if (isNumberNaN(limit)) return input;
 
     if (isNumber(input)) input = input.toString();
     if (!isArray(input) && !isString(input)) return input;
diff --git a/src/ng/rootScope.js b/src/ng/rootScope.js
index 71a82dcda547..1dde94a182f8 100644
--- a/src/ng/rootScope.js
+++ b/src/ng/rootScope.js
@@ -768,8 +768,7 @@ function $RootScopeProvider() {
                     if ((value = watch.get(current)) !== (last = watch.last) &&
                         !(watch.eq
                             ? equals(value, last)
-                            : (typeof value === 'number' && typeof last === 'number'
-                               && isNaN(value) && isNaN(last)))) {
+                            : (isNumberNaN(value) && isNumberNaN(last)))) {
                       dirty = true;
                       lastDirtyWatch = watch;
                       watch.last = watch.eq ? copy(value, null) : value;