Solution: The GCF of 126 and 4 is 2MethodsHow to find the GCF of 126 and 4 using Prime FactorizationOne way to find the GCF of 126 and 4 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 126?What are the Factors of 4?Here is the prime factorization of 126:21×32×712^1 × 3^2 × 7^121×32×71And this is the prime factorization of 4:222^222When 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 126 and 4 by multiplying all the matching prime factors to get a GCF of 126 and 4 as 4:Thus, the GCF of 126 and 4 is: 4How to Find the GCF of 126 and 4 by Listing All Common FactorsThe first step to this method of finding the Greatest Common Factor of 126 and 4 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, 126 and 4:Factors of 126: 1, 2, 3, 6, 7, 9, 14, 18, 21, 42, 63, 126Factors of 4: 1, 2, 4When you compare the two lists of factors, you can see that the common factor(s) are 1, 2. Since 2 is the largest of these common factors, the GCF of 126 and 4 would be 2.Find the GCF of Other Number PairsWant more practice? Try some of these other GCF problems:What is the GCF of 11 and 17?What is the GCF of 102 and 93?What is the GCF of 94 and 48?What is the GCF of 32 and 60?What is the GCF of 73 and 55?