Learn about prime numbers, factors and multiples with BBC ... This can be done by listing the factor pairs as successive branches in a factor tree. ... Which number is a factor of \({18}\), but ...

The prime factors in the factor tree are circled. Write 108 as a product of its prime factors. The prime factors are written in numerical order: 108 = 2 × 2 × 3 × 3 × 3.