When it comes to understanding numbers, one fundamental concept is factoring. Factors of a number are whole numbers that can be multiplied together to produce that number. In the case of the number 18, factors are the numbers that, when multiplied together, result in 18.

**18 is a positive integer with a total of 6 factors: 1, 2 3, 6, 9, and 18.**

In this post, we will learn how to find those factors of 18.

## How to Factorize 18

To find the factors, divide 18 by all whole numbers starting with 1. Stop when the result is smaller than the number you are dividing by. Only results that include whole numbers are factors.

These are all the positive integer pairs that can be multiplied to give you the product of 18. So, the factors of 18 are 1, 2, 3, 6, 9, and 18.

Rules:

- Even numbers are always divisible by 2
- If a number ends in 0 or 5, it is divisible by 5

## Factors of 18 in Pairs

**Factor pairs are the two numbers that can be multiplied to make the product, 18. **All factor pairs for 18 are as follows:

- 1 × 18 = 18
- 2 × 9 = 18
- 3 × 6 = 18

These positive factors are the most commonly accepted answer; however, there are also negative factors of 18.

**The negative factors of 18 are: -1, -2, -3, -6,-9, -18**

The negative factor pairs of 18 are:

- -1 × -18 = 18
- -2 × -9 = 18
- -3 ×- 6 = 18

## Prime Factorization of 18

Now that we’ve identified the factors, let’s take it a step further and find the prime factorization of 18.

To understand prime factors, you must know about prime numbers. **A prime number (3, 5, 17, 23, etc.) is a number that is greater than 1 and cannot be divided into smaller numbers.** (They can only be divided by 1 and the number itself.)

Prime factorization is when a product is broken down into all of its prime factors.

The prime factorization of 18 is:

- 2 x 3 x 3 = 18

To get this number, we start with the smallest prime factor that 18 is divisible by: 2.

- 18 ÷ 2 = 9 (
*9 is not a prime number, so we continue*) - 9 ÷ 3 = 3 (
*3 is a prime number*)

So, the prime factorization of 18 is 2 × 3 × 3.

It can also be written as exponents.

**The prime factors of 18 are: 2 x 3 x 3 = 2 × 3 ^{2} = 18**

## Common Factors of 18

The **common factors of two (or more) numbers are the factors that the numbers have in common**. For example:

The factors of 18 are: 1, 2, 3, 6, 9, 18

The factors of 27 are: 1, 3, 9, 27

Their common factors are: 1, 3 and 9

The **greatest common factor** is the largest of the common factors. For 18 and 27, the GCF is 9.

- What is the greatest common factor of 18 and 24?

The factors of 18 are: 1, 2, 3, 6, 9, 18

The factors of 24 are: 1, 2, 3, 4, 6, 8, 12, 24

The greatest common factor is: 6

- What is the greatest common factor of 18 and 12?

The factors of 18 are: 1, 2, 3, 6, 9, 18

The factors of 12 are: 1, 2, 3, 4, 6, 8, 12

The greatest common factor is: 6

## Related:

What are the factors of 24?

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