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In this lesson, you will learn about factors, square numbers and prime numbers.

This lesson includes:

  • a video
  • a learning summary
  • three activities



A factor is a number that divides into another number exactly and without leaving a remainder.

The number 12 has six factors:

1, 2, 3, 4, 6 and 12

If 12 is divided by any of the six factors then the answer will be a whole number.

For example: 12 ÷ 3 = 4

Watch this short video from BBC Bitesize to find out more.

Find out how to work out the factors of a number using eggs!

Square numbers

Square numbers are formed by multiplying a number by itself. All square numbers have an odd number of factors. For example, the number 25 has three factors:

1, 5 and 25

And the number 16 has five factors:

1, 2, 4, 8 and 16

Prime numbers

A prime number is a number which is only divisible by 1 and itself. Prime numbers cannot be divided by another number to leave a whole number.

Prime numbers include:

2, 3, 5, 7, 11, 13, 17, 19, 23 and 29.

The number 59 is prime because it is only divisible by 1 and 59.

The number 51 is not prime because it is divisible by 3 and 17 as well as 1 and 51.

The number 1 only has one factor (itself). Therefore, 1 is not a prime number.


Activity 1


Find out how much you know about factors in this short quiz!

Activity 2

Find the factors

Have a go at this interactive activity from My Maths, Oxford University Press.
Find the factors of different numbers.

Watch out - if you select two incorrect answers it's game over!

Find the factors

Activity 3

Worksheet: Factors

Have a go at this worksheet from Whizz Education.

You can print it out or write your answers on a piece of paper.


There's more to learn

Have a look at these other resources around the BBC and the web.

KS3 Maths
BBC Bitesize Daily
The BBC Bitesize 14 day sort-your-life-out challenge
11 - 14 Maths
KS3 English
Simon Singh's Numbers