Understanding the factors of a number is a key part of learning and enjoying math. Factors are the numbers that evenly divide another number without leaving a remainder. In this case, we'll explore the factors of the number 21, a common number that we often come across in our daily lives. This will help us better understand how to identify and use factors in real-world scenarios.

## What Are The Factors Of 21?

When we talk about the factors of 21, we are looking for the numbers that can be multiplied together to get 21. For example, if we think of two numbers that equal 21 when multiplied, those numbers are both factors of 21.

## List Of The Factors Of 21

Here are the factors of 21:

- 1
- 21
- 3
- 7

## How To Calculate The Factors Of 21

Calculating the factors of 21 involves finding all the whole numbers that can be multiplied together to produce 21. To do this, we can use two main methods: the multiplication method and the division method.

## The Multiplication Method

Using the multiplication method, we list pairs of numbers that, when multiplied together, equal 21:

- Start with the number 1 and 21 because 1 multiplied by 21 equals 21.
- Next, try 2. Since 2 cannot multiply with any whole number to get 21, we move on to the next number.
- Next is 3. Multiply 3 by 7 to get 21.
- Continue this until we can't find more pairs. Therefore, the factor pairs of 21 are:
- 1 and 21
- 3 and 7

## The Division Method

The division method involves dividing 21 by a series of whole numbers to see if the result is a whole number. If it is, both the divisor and the result are factors.

- Start by dividing 21 by 1. The answer is 21, so both 1 and 21 are factors.
- Next, divide 21 by 2. Since the result is not a whole number, 2 is not a factor.
- Divide 21 by 3. The answer is 7, so both 3 and 7 are factors.
- Continue this process up to the square root of 21 (approximately 4.58).

Ultimately, the factors we get are 1, 3, 7, and 21.

## What Is Prime Factorization?

Prime factorization is the process of breaking down a number into its prime factors. Prime factors are prime numbers that, when multiplied together, equal the original number. For any given number, there is a unique set of prime factors.

## Prime Factors Of 21

The prime factors of 21 are:

- 3
- 7

Both 3 and 7 are prime numbers, and they multiply together to give 21.

## Conclusion

Understanding factors, how to calculate them using multiplication and division methods, and recognizing prime factors helps us in many mathematical tasks. It strengthens our number sense and can aid in solving more complex problems. The number 21 has been broken down into its basic components, making it easier to understand and work with.

## FAQs

**Q: What is the largest factor of 21?**

A: The largest factor of 21 is 21 itself.

**Q: Are 2 and 5 factors of 21?**

A: No, both 2 and 5 are not factors of 21 because they do not divide 21 evenly.

**Q: Is 21 a prime number?**

A: No, 21 is not a prime number because it has factors other than 1 and itself, specifically 3 and 7.

**Q: Can a negative number be a factor of 21?**

A: In mathematics, when we talk about factors, we usually refer to positive whole numbers. However, technically, negative numbers could also be factors, such as -1, -3, -7, and -21.

**Q: What is the difference between a factor and a multiple?**

A: A factor is a number that divides another number evenly, while a multiple is the result of multiplying that number by an integer. For example, 3 is a factor of 21, and 21 is a multiple of 3.