JQuery .isNumeric
according to http://api.jquery.com/jQuery.isNumeric/
it's :jQuery.isNumeric(value)
so, it should be $.isNumeric($("#EmpNum").val())
Pass in the value as an argument to isNumeric. Also make sure you are using jQuery version 1.7 as this was added in 1.7.
$.isNumeric( $('#EmpNum').val() )