What is the pime factorization and gcf of 12?

The prime factorization of 12 is: 2 x 2 x 3 = 12

However, there cannot be a greatest common factor (GCF) of just one number. To be common there need to be at least two numbers. If you find all the factors of two or more numbers, and you find some factors are the same ("common"), then the largest of those common factors is the Greatest Common Factor.