We say that a number is composite if it has a factor other than 1 and itself. In this article, we list out all the composite numbers between 21 and 40. We then explain why this list includes all the composite numbers lying in between.

**List of composite numbers:**

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

**Why is this the entire list of composite numbers between 21 and 40?**

- 21 is composite because it has factors 1, 3, 7 and 21.
- 22 is composite because it has factors 1, 2, 11 and 22.
- 23 is prime because it has only two factors – 1 and 23.
- 24 is composite because it has factors 1, 2, 3, 4, 6, 8, 12 and 24.
- 25 is composite because it has factors 1, 5 and 25.
- 26 is composite because it has factors 1, 2, 13 and 26.
- 27 is composite because it has factors 1, 3, 9 and 27.
- 28 is composite because it has factors 1, 2, 4, 7, 14 and 28.
- 29 is prime because it has only two factors – 1 and 29.
- 30 is composite because it has factors 1, 2, 3, 5, 6, 10, 15 and 30.
- 31 is prime because it has only two factors – 1 and 31.
- 32 is composite because it has factors 1, 2, 4, 8, 16 and 32.
- 33 is composite because it has factors 1, 3, 11 and 33.
- 34 is composite because it has factors 1, 2, 17 and 34.
- 35 is composite because it has factors 1, 5, 7 and 35.
- 36 is composite because it has factors 1, 2, 3, 4, 9, 12, 18 and 36.
- 37 is prime because it has only two factors – 1 and 37.
- 38 is composite because it has factors 1, 2, 19 and 38.
- 39 is composite because it has factors 1, 3, 13 and 39.
- 40 is composite because it has factors 1, 2, 4, 5, 8, 10, 20 and 40.