Year 9: Special numbers

This cheat-sheet covers key concepts related to special numbers.

Prime Numbers

A prime number is a whole number greater than 1 that has only two divisors: 1 and itself.

• Examples: 2, 3, 5, 7, 11, 13, 17, 19, etc.
• To test if a number is prime, divide it by all prime numbers up to the square root of the number.

Composite Numbers

A composite number is a whole number greater than 1 that has more than two divisors. It can be expressed as a product of prime numbers.

• Examples: 4, 6, 8, 9, 10, 12, etc.

Square Numbers

A square number is the result of squaring an integer (a whole number).

• Examples: 1, 4, 9, 16, 25, 36, etc.
• These are often represented with the ‘²’ symbol. e.g., 5² = 25

Perfect Squares

A perfect square is a number that is the square of an integer. This is the same as a square number.

Perfect Cubes

A perfect cube is a number that is the cube of an integer.

• Examples: 1, 8, 27, 64, 125, etc.
• These are often represented with the ‘³’ symbol. e.g., 3³ = 27