Question: what is the greatest common factor 12 and 66?
Answer: The prime factorization of 12 is: 2 x 2 x 3. The prime factorization of 66 is: 2 x 3 x 11. The prime factors and multiplicities 12 and 66 have in common are: 2 x 3. 2 x 3 is the gcf of 12 and 66. gcf(12,66) = 6.