Factor
A whole number that divides exactly into another number.
Opening Maths Unlocked
Preparing the next page…
Opening Maths Unlocked
Preparing the next page…
GCSE MATHS PRACTICE
Prime factorisation writes a whole number greater than 1 as a product of prime numbers. Draw a factor tree: split a composite number into two factors, then split any composite factors again until every endpoint is prime. Different valid trees give the same prime factorisation. Try one example and four questions before continuing in the app.
Updated 8 October 2026
A whole number that divides exactly into another number.
A factor that is prime: it has exactly two positive factors, 1 and itself.
Writing a number as a product of primes, using indices for repeated factors.
Use a factor tree to write 90 as a product of prime factors.
Answer: 90 = 2 × 3² × 5
Write 42 as a product of prime factors.
Write 108 as a product of prime factors, using index notation.
A factor tree for 140 begins with 14 × 10. Complete the prime factorisation in index notation.
A number has prime factorisation 2³ × 3 × 7. What is the number?