Divisibility Rules

There are times when knowing whether a number is divisible by another number can be helpful. For instance, if you want to pack 219 cookies into bags containing 3 cookies each without any cookie leftover, you will need to know whether 219 is divisible by 3.

You can tell whether a number is divisible by 3 by doing this:
- Add up the digits.
- If the sum is divisible by 3, then the number is divisible by 3.

In our example, 219 is divisible by 3 because 2+1+9=12, and 12 is divisible by 3.

The other divisibility rules that you might find useful are as follows.

1. A number is divisible by 2 if the last digit is even.
2. A number is divisible by 3 if the sum of the digits is divisible by 3.
3. A number is divisible by 4 if the number formed by the last two digits is divisible by 4.
4. A number is divisible by 5 if the last digit is 0 or 5.
5. A number is divisible by 6 if the number is divisible by 2 and 3.
6. A number is divisible by 8 if the number formed by the last 3 digits is divisible by 8.
7. A number is divisible by 9 if the sum of the digits is divisible by 9.
8. A number is divisible by10 if the last digit is 0.