INT numbers?

[ligraci]

Hi to all!!
I need something that allows me to know if a number can be divided by 15 without rest. I need to do an operation every 15 times, so if MYNUMBER/15 is 1 or 2 or 3 and so on I do the operation else not.

How can I know this?

Thanks! ^_

[Quevas]

if($yourNumber%15!=0) ...

Means:
if my number divided by 15 returns rest ...