Question

What is the composite number between 20 and 40?

Answer 1

All of the following are composite:

`20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40`

Explanation:

A composite number is any number which has factors apart from `1` and itself.

So most numbers between `20` and `40` are composite:

`20 = 2xx2xx5`

`21 = 3xx7`

`22 = 2xx11`

`24 = 2xx2xx2xx3`

`25 = 5xx5`

`26 = 2xx13`

`27 = 3xx3xx3`

`28 = 2xx2xx7`

`30 = 2xx3xx5`

`32 = 2xx2xx2xx2xx2`

`33 = 3xx11`

`34 = 2xx17`

`35 = 5xx7`

`36 = 2xx2xx3xx3`

`38 = 2xx19`

`39 = 3xx13`

`40 = 2xx2xx2xx5`

The only prime numbers (having no factors apart from `1` and themselves) between `20` and `40` are: `23, 29, 31, 37`.