diff --git a/src/English/CardinalNumeral.php b/src/English/CardinalNumeral.php
index 4cff7fc..1a8c0e7 100644
--- a/src/English/CardinalNumeral.php
+++ b/src/English/CardinalNumeral.php
@@ -36,11 +36,11 @@ class CardinalNumeral extends NumeralCreation {
     );
 
     static public $exponents = array(
-        100 => 'hundred',
-        1000 => 'thousand',
-        1000000 => 'million',
-        1000000000 => 'billion',
-        1000000000000 => 'trillion',
+        '100' => 'hundred',
+        '1000' => 'thousand',
+        '1000000' => 'million',
+        '1000000000' => 'billion',
+        '1000000000000' => 'trillion',
     );
 
     static public function getCases($number) {}
diff --git a/src/Russian/CardinalNumeral.php b/src/Russian/CardinalNumeral.php
index 52e1968..c4b31ff 100644
--- a/src/Russian/CardinalNumeral.php
+++ b/src/Russian/CardinalNumeral.php
@@ -50,10 +50,11 @@ class CardinalNumeral extends NumeralCreation implements Cases {
     );
 
     static protected $exponents = array(
-        1000 => 'тысяча',
-        1000000 => 'миллион',
-        1000000000 => 'миллиард',
-        1000000000000 => 'триллион',
+        '1000' => 'тысяча',
+        '1000000' => 'миллион',
+        '1000000000' => 'миллиард',
+        '1000000000000' => 'триллион',
+        '1000000000000000' => 'квадриллион',
     );
 
     static protected $precalculated = array(