A prime number is a whole number that has exactly two factors: itself and \(1\).

For example, \(2\) only has the factors of \(1\) and \(2\) (it can only be divided evenly by \(1\) and \(2\)), so it is a prime number.

The diagram shows the prime numbers between \(1\) and \(100\), shaded in green.

Numbers which can be divided evenly by numbers other than themselves and \(1\) are called composite numbers. For example, \(15 = 5 \times 3\) is a composite number.

Note that \(1\) is neither prime nor composite.