Prime and Composite Numbers

A prime number has exactly two factors, 1 and itself; a composite number has more than two. In NSW Year 7 maths (NESA outcome MA4‑IND‑C‑01) recognising primes quickly is the starting point for prime factors, HCF and LCM.

You will list factor pairs, explain why 1 is neither prime nor composite and why 2 is the only even prime, use divisibility tests to decide whether numbers such as 91 are prime, list the primes between 40 and 60, and explore twin primes, perfect numbers and Goldbach's idea. Arranging chairs in equal rows is a real example. It is part of Year 7 Whole Numbers.