what is the greatest common factor between 69 and 21?
['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.']