Question: what is the greatest common factor between 69 and 21?
Answer: The prime factorization of 21 is: 3 x 7.
The prime factorization of 69 is: 3 x 23.
The prime factors and multiplicities 21 and 69 have in common are: 3.
3 is the gcf of 21 and 69.
gcf(21,69) = 3.