When discussing the factors of a number, we refer to the whole numbers that divide evenly into that number without leaving a remainder. The factors of 21 are the numbers that can be multiplied together to give the product 21. Let’s explore the factors of 21:

- Number 1: 1 is a factor of every number, including 21.
- Number 3: 3 is a factor of 21 because 3 multiplied by 7 equals 21.
- Number 7: 7 is a factor of 21 because 7 multiplied by 3 equals 21.
- Number 21: 21 is a factor of itself.

So, the factors of 21 are 1, 3, 7, and 21. These numbers evenly divide into 21, with no remainder.

## How many Factors of 21

To determine the total number of factors of 21, we can simply count the factors listed in the previous response. In the case of 21, there are four factors:

1, 3, 7, and 21.

Therefore, 21 has a total of four factors.

#### Factor Pairs of 21

Factor pairs of a number are the pairs of factors that, when multiplied together, give the original number. In the case of 21, the factor pairs are as follows:

1 x 21 = 21

3 x 7 = 21

So, the factor pairs of 21 are (1, 21) and (3, 7).

#### All Factors of 21 using Multiplication

To find all the factors of 21 using multiplication, we can start with the factor pairs we previously identified: (1, 21) and (3, 7). Then, we can generate additional factors by multiplying these pairs by other whole numbers:

1 x 21 = 21

3 x 7 = 21

By multiplying these factor pairs, we obtain the following factors of 21:

1, 3, 7, 21

These are all the factors of 21 that can be obtained through multiplication.