Divisibility rules 3 6 and 9

If you add all of the digits of a number, and it's divisible by 3, the entire number will be divisible by 3. If the number is divisible by 2 and 3, it's divisible by 6 as well. If the digits of a number add up to a number divisible by 9, the whole number will be divisible by 9.

3 - the sum of the digits is divisible by 3

6 - the number is both divisible by both 3 and 2

9 - the sum of the digits is divisible by 9