what is the least common multiple of 12 and 21 using prime factorization?
Alternatively, the lcm of 12 and 21 can be found using the prime factorization of 12 and 21: The prime factorization of 12 is: 2 x 2 x 3. The prime factorization of 21 is: 3 x 7. Eliminate the duplicate factors of the two lists, then multiply them once with the remaining factors of the lists to get lcm(12,12) = 84.