What is a factor?

Factors

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

• Most numbers have an even number of factors; however, a square number has an odd number of factors.

• A prime number has only two factors - the number itself and 1.

Factors

The factors of a number are the numbers that divide into it exactly. 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

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

Because 25 is a square number it has an odd number of factors.

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 1 only has one factor (itself); therefore, 1 is not a prime number.

Factors quiz

Test your knowledge of factors with this quick quiz.

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