## Prime Factorisation

A **prime number** is a positiveinteger, larger than 1, which cannot be expressed as the product of two smaller positiveintegers.

Examples of prime numbers are 2 (the only even prime number), 3, 5, 7, 11, 13, 17, 19, 23 and 29.

Examples of numbers that are *not* prime numbers are 4 (as 2x2=4), 6 (as 3x3=4) and 8 (as 2x4=8).

To **prime factorise** a number means to write the number as a product of prime numbers.