Question: what is the least common multiple of 12 and 21 using prime factorization?
Answer: 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.