diff --git a/web/org.openbravo.mobile.core/source/utils/ob-arithmetic.js b/web/org.openbravo.mobile.core/source/utils/ob-arithmetic.js
--- a/web/org.openbravo.mobile.core/source/utils/ob-arithmetic.js
+++ b/web/org.openbravo.mobile.core/source/utils/ob-arithmetic.js
@@ -19,8 +19,12 @@
     return new BigDecimal(a.toString());
   };
 
+  var isNumber = function(a) {
+    return toString.call(a) === '[object Number]';
+  };
+
   var toNumber = function(big, arg_scale) {
-    var localscale = _.isNumber(arg_scale) ? arg_scale : scale;
+    var localscale = isNumber(arg_scale) ? arg_scale : scale;
     if (big.scale) {
       return parseFloat(big.setScale(localscale, roundingmode).toString(), 10);
     } else {
@@ -63,7 +67,7 @@
     return toNumber(
       toBigDecimal(a).divide(
         toBigDecimal(b),
-        _.isNumber(arg_scale) ? arg_scale : scale,
+        isNumber(arg_scale) ? arg_scale : scale,
         roundingmode
       ),
       arg_scale