MEPX
Chapter 5 of 10All chapters
  1. 1Finding the rule
  2. 2Arithmetic sequences
  3. 3Geometric sequences
  4. 4Sequences worth knowing
  5. 5Primes and factors
  6. 6Writing the nth term
  7. 7Patterns from shapes
  8. 8Recursive rules
  9. 9Patterns outside mathematics
  10. 10Solving pattern puzzles

Chapter 5 of 10

Primes and factors

The building blocks.

What primes are

A prime has exactly two factors: itself and one. That is why one is not prime, and two is the only even prime.

  • Every whole number breaks into a unique set of prime factors.
  • Primes thin out as numbers grow, but never run out.

Why they matter

Prime factorisation underpins fractions, common denominators and modern encryption, which relies on multiplying two large primes being easy and undoing it being hard.