Factors of 20
Every whole number that divides 20 exactly, the factor pairs, and how to find them yourself.
The answer
The factors of 20 are 1, 2, 4, 5, 10 and 20.
Factor pairs of 20
| Pair | Makes |
|---|---|
| 1 × 20 | 20 |
| 2 × 10 | 20 |
| 4 × 5 | 20 |
Prime factors of 20
- Prime factorisation
- 20 = 2 × 2 × 5 (2² × 5)
- Reading index form
- A small raised number tells you how many times to use that factor. For example, 2³ means 2 × 2 × 2.
- Is 20 prime?
- No. It has 6 factors, not just 1 and 20.
- Is 20 a square number?
- No. 4 × 4 = 16 and 5 × 5 = 25, so 20 falls between two square numbers.
How to find the factors of 20
20 is even, so 2 is sure to be a factor. It ends in 0, so 5 is a factor. Work up from 1 to 4, and write down both numbers in every pair you find.
- 20 ÷ 1 = 20, so 1 × 20 is a pair.
- 20 ÷ 2 = 10, so 2 × 10 is a pair.
- 3 does not go into 20 exactly.
- 20 ÷ 4 = 5, so 4 × 5 is a pair.
Stop at 5: 5 × 5 = 25, which is more than 20. The next pair you would find is 5 × 4, which is 4 × 5 turned round, so you already have every pair.
20 in the times tables
2 × 10 = 20 and 4 × 5 = 20. Practise the 2 times table, 4 times table, 5 times table and 10 times table.
More numbers
Check whether 20 is prime.
Questions parents ask
What is the largest factor of 20, apart from 20 itself?
10. Divide 20 by its smallest factor above 1, which is 2: 20 ÷ 2 = 10.
What do the factors of 20 add up to?
42. Leaving out 20 itself, they add up to 22, which is more than 20, so 20 is called an abundant number.
Which number after 20 has the same number of factors?
28. Like 20, it has exactly 6 factors.
Continue your number practice
Explore the diagnostic for another set of practice questions.