function checkPrime(pass) {
var i;
var factors = 0;
var num = eval(pass.num.value);
var ceiling = Math.sqrt(num);
while (i++ < ceiling) {
if (num % i == 0) {
factors = 1;
}
}
document.open();
document.write("
");
if (factors > 0)
document.write(num, " isn't a prime");
else if (factors == 0)
document.write(num, " is a prime");
document.write(" ");
document.close();
}