Rules Of Numbers Divisibility.

Number is divisible by 3 if the sum of it`s digits is also divisible by 3. For instance 528. 5+2+8=15. 15 is divisible by 3, thus 528 is also divisible by 3.

The similar rules applied to check if the number is divisible by 9. In this case the sum of it`digits must be divisible by 9. For example 5553. 5+5+5+3=18. 18 is divisible by 9, so 5552 is also divisible by 9

If the number is even and sum of it`s digits is divisible by 6, then the whole number is also divisible by 6.

Example: 624. 6+2+4 =12 is divisible by 3 and 624 is even number, thus it`s divisible by 6.

But if you take , for example 621, even though the sum of it`s digits(6+2+1=9) is divisible by 3, since 621 is odd number, it`s not divisible by 6.