Probably not the answer that anybody is looking for, but you can easily do this question without any programming.

First, find the prime factors of each number 1 through 20, then find the LCM of the numbers.

This would then give us, 2⁴ x 3² x 5 x 7 x 11 x 13 x 17 x 19

Which is the final answer 232792560.