2  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
2  1 1 3 2 5 3 7 4 9  5 11  6 13  7 15  8 17  9 19 10
2  1 1 3 1 5 3 7 2 9  5 11  6 13  7 15  4 17  9 19  5
2  1 1 3 1 5 3 7 1 9  5 11  3 13  7 15  2 17  9 19  5
3  1 1 3 1 5 3 7 1 9  5 11  3 13  7 15  1 17  9 19  5
3  1 1 1 1 5 1 7 1 3  5 11  1 13  7  5  1 17  3 19  5
5  1 1 1 1 5 1 7 1 1  5 11  1 13  7  5  1 17  1 19  5
7  1 1 1 1 1 1 7 1 1  1 11  1 13  7  1  1 17  1 19  1
11 1 1 1 1 1 1 1 1 1  1 11  1 13  1  1  1 17  1 19  1
13 1 1 1 1 1 1 1 1 1  1  1  1 13  1  1  1 17  1 19  1
17 1 1 1 1 1 1 1 1 1  1  1  1  1  1  1  1 17  1 19  1
19 1 1 1 1 1 1 1 1 1  1  1  1  1  1  1  1  1  1 19  1
   1 1 1 1 1 1 1 1 1  1  1  1  1  1  1  1  1  1  1  1

Multiply all the numbers on the leftmost column and you have
the number that can be evenly divided by all numbers
between 1 - 20.

The number comes to 232792560.