A

**prime number**is a whole**number**greater than 1 whose only factors are 1 and itself. A factor is a whole**numbers**that can be divided evenly into another**number**. The first few**prime numbers**are 2, 3, 5, 7, 11, 13, 17, 19, 23 and 29.So, what is the prime number of 21?

When a

**number**has more than two**factors**it is called a composite**number**. Here are the first few**prime numbers**: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, etc.What are all of the multiples of 21?

Answer : 21,42,63,84,105,126,147,168,189,210,231,252,273,294,315,336,357,378,399,420,441,462,483,504,525,546,567,588,609,630,651,672,693,714,735,756,777,798,819,840,861,882,903,924,945,966,987,1008,1029, Related Links : What are the

**factors**of 21?What is the prime factors of 20?

**20**is a composite

**number**.

**20**= 1 x

**20**, 2 x 10, or 4 x 5.

**Factors**of

**20**: 1, 2, 4, 5, 10,

**20**.

**Prime factorization**:

**20**= 2 x 2 x 5, which can also be written

**20**= 2² x 5.