$$1 \times 2 \times 3 \times 4 \times 5 \times 6 \times 7 \times 8 \times 9 \times 10 \times 11 \times 12 \times 13 \times 14 \times 15 \times 16 \times 17 \times 18 \times 19 \times 20$$
$2432902008176640000$
$2^{18}\times 3^{8}\times 5^{4}\times 7^{2}\times 11\times 13\times 17\times 19$
