A divisibility rule is a shortcut way of working out whether an integer is divisible by a fixed divisor without actually having to carry out the division! We can do this by examining the digits. Below is a summary table containing rules for the divisors 2,3,4,5,6,9,10.

Let me give you an example. If you want to know if the integer 653337 is divisible by 3, simply take the SUM of the digits, 6+5+3+3+3+7=27 and check if it’s divisible by ‘3’.  If it is, then the integer is divisble by 3! Cool isn’t it!