Solution: The GCF of 63 and 140 is 7MethodsHow to find the GCF of 63 and 140 using Prime FactorizationOne way to find the GCF of 63 and 140 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 63?What are the Factors of 140?Here is the prime factorization of 63:32×713^2 × 7^132×71And this is the prime factorization of 140:22×51×712^2 × 5^1 × 7^122×51×71When 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 63 and 140 by multiplying all the matching prime factors to get a GCF of 63 and 140 as 49:Thus, the GCF of 63 and 140 is: 49How to Find the GCF of 63 and 140 by Listing All Common FactorsThe first step to this method of finding the Greatest Common Factor of 63 and 140 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, 63 and 140:Factors of 63: 1, 3, 7, 9, 21, 63Factors of 140: 1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 70, 140When you compare the two lists of factors, you can see that the common factor(s) are 1, 7. Since 7 is the largest of these common factors, the GCF of 63 and 140 would be 7.Find the GCF of Other Number PairsWant more practice? Try some of these other GCF problems:What is the GCF of 45 and 23?What is the GCF of 125 and 75?What is the GCF of 150 and 144?What is the GCF of 11 and 149?What is the GCF of 92 and 6?