It's very simple! You probably already know that a number is divisible by another if the remainder of their division is 0. The MOD operator returns this remainder, so you can do something as simple as...
NUM1 MOD NUM2 == 0
...to check if NUM1 is divisible by NUM2.
Please be aware that the MOD operator only works with whole numbers (integers) and possibly only positive numbers. If you try using decimal values, they will be rounded off first. If you really need it to work with decimals, you can probably develop a custom algorithm pretty easily.
