Solution: The GCF of 4 and 28 is 4MethodsHow to find the GCF of 4 and 28 using Prime FactorizationOne way to find the GCF of 4 and 28 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 4?What are the Factors of 28?Here is the prime factorization of 4:222^222And this is the prime factorization of 28:22×712^2 × 7^122×71When 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 4 and 28 by multiplying all the matching prime factors to get a GCF of 4 and 28 as 4:Thus, the GCF of 4 and 28 is: 4How to Find the GCF of 4 and 28 by Listing All Common FactorsThe first step to this method of finding the Greatest Common Factor of 4 and 28 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, 4 and 28:Factors of 4: 1, 2, 4Factors of 28: 1, 2, 4, 7, 14, 28When you compare the two lists of factors, you can see that the common factor(s) are 1, 2, 4. Since 4 is the largest of these common factors, the GCF of 4 and 28 would be 4.Find the GCF of Other Number PairsWant more practice? Try some of these other GCF problems:What is the GCF of 125 and 95?What is the GCF of 29 and 13?What is the GCF of 72 and 84?What is the GCF of 88 and 147?What is the GCF of 59 and 149?