Solution: The GCF of 132 and 21 is 3
Methods
How to find the GCF of 132 and 21 using Prime Factorization
One way to find the GCF of 132 and 21 is to compare the prime factorization of each number. To find the prime factorization, you can follow the instructions for each number here:
What are the Factors of 132?
What are the Factors of 21?
Here is the prime factorization of 132:
2
2
×
3
1
×
1
1
1
2^2 × 3^1 × 11^1
2 2 × 3 1 × 1 1 1
And this is the prime factorization of 21:
3
1
×
7
1
3^1 × 7^1
3 1 × 7 1
When you compare the prime factorization of these two numbers, you can see that there are matching prime factors. You can now find the Greatest Common Factor of 132 and 21 by multiplying all the matching prime factors to get a GCF of 132 and 21 as 9:
Thus, the GCF of 132 and 21 is: 9
How to Find the GCF of 132 and 21 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 132 and 21 is to find and list all the factors of each number. Again, you can see how this is done by looking at the “Factors of” articles that are linked to above.
Let’s take a look at the factors for each of these numbers, 132 and 21:
Factors of 132: 1, 2, 3, 4, 6, 11, 12, 22, 33, 44, 66, 132
Factors of 21: 1, 3, 7, 21
When you compare the two lists of factors, you can see that the common factor(s) are 1, 3. Since 3 is the largest of these common factors, the GCF of 132 and 21 would be 3.
Find the GCF of Other Number Pairs
Want more practice? Try some of these other GCF problems:
What is the GCF of 119 and 127?
What is the GCF of 146 and 95?
What is the GCF of 48 and 83?
What is the GCF of 2 and 59?
What is the GCF of 72 and 86?