Question: what is the greatest common factor between 63 and 99?
Answer: The prime factorization of 63 is: 3 x 3 x 7. The prime factorization of 99 is: 3 x 3 x 11. The prime factors and multiplicities 63 and 99 have in common are: 3 x 3. 3 x 3 is the gcf of 63 and 99. gcf(63,99) = 9.