<!-- Begin
function calculate(form) {
var num=parseInt(form.number.value);
if (isNaN(num) || num < 0) {
form.result.value=(form.number.value + " is not a valid number!  Try again!");
}
if (num == 1 || num == 2) {
form.result.value=(num + " is prime!");
}
for (var i=2;i<num;i++) {
if (num % i == 0) {
var prime="yes";
form.result.value=(num + " is not prime.  It is divisible by " + i + ".");
break;
}
if (num % i != 0) var prime="no";
}
if (prime == "no") form.result.value=(num + " is prime!");
} 
// End -->