It is very useful when we look at a number if we can identify which numbers it is divisible by. This means numbers that divide it without a remainder.

All even numbers are divisible by 2, so if a number ends with 2, 4, 6, 8 or 0, it is divisible by 2. Conversely, odd numbers are not divisible by 2, so if a number ends with 1, 3, 5, 7 or 9, then it is not divisible by 2.

Let’s use the following exercise to try and identify some other divisibility rules ourself:

Exercise 1

Divisibility rules

Copy these down into your notebook to help you remember them:

Worked Example

Check to see whether 237 is a prime number.

Exercise 2

Answers to both exercises