Factors of 90

Every whole number that divides 90 exactly, the factor pairs, and how to find them yourself.

The answer

The factors of 90 are 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45 and 90.

Factor pairs of 90

Pair	Makes
1 × 90	90
2 × 45	90
3 × 30	90
5 × 18	90
6 × 15	90
9 × 10	90

Prime factors of 90

Prime factorisation: 90 = 2 × 3 × 3 × 5 (2 × 3² × 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 90 prime?: No. It has 12 factors, not just 1 and 90.
Is 90 a square number?: No. 9 × 9 = 81 and 10 × 10 = 100, so 90 falls between two square numbers.

How to find the factors of 90

90 is even, so 2 is sure to be a factor. Its digits add up to 9, a multiple of 9, so 3 and 9 are factors. It ends in 0, so 5 is a factor. Work up from 1 to 9, and write down both numbers in every pair you find.

90 ÷ 1 = 90, so 1 × 90 is a pair.
90 ÷ 2 = 45, so 2 × 45 is a pair.
90 ÷ 3 = 30, so 3 × 30 is a pair.
4 does not go into 90 exactly.
90 ÷ 5 = 18, so 5 × 18 is a pair.
90 ÷ 6 = 15, so 6 × 15 is a pair.
7 does not go into 90 exactly.
8 does not go into 90 exactly.
90 ÷ 9 = 10, so 9 × 10 is a pair.

Stop at 10: 10 × 10 = 100, which is more than 90. The next pair you would find is 10 × 9, which is 9 × 10 turned round, so you already have every pair.

90 in the times tables

5 × 18 = 90, 6 × 15 = 90 and 9 × 10 = 90. Practise the 9 times table, 10 times table, 15 times table and 18 times table.

More numbers

Check whether 90 is prime.

Questions parents ask

What is the largest factor of 90, apart from 90 itself?

45. Divide 90 by its smallest factor above 1, which is 2: 90 ÷ 2 = 45.

What do the factors of 90 add up to?

234. Leaving out 90 itself, they add up to 144, which is more than 90, so 90 is called an abundant number.

Which number after 90 has the same number of factors?

96. Like 90, it has exactly 12 factors.

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