A number is divisible by another when the remainder after division by that number is zero.
No its not
... when the remainder after division ...
Its the remainder
The remainder is zero, yes.
Do the division and if the remainder is 0 then the number is divisible by the something and if not it isn't.
yes, this just says that there is a 0 remainder. For example, 6 is divisible by 3 since the remainder is 0
You need to carry out the division. If the remainder is 0 then it is divisible, if not it is not. There are divisibility rules which can help with small or simple divisors but these are quite limited.