Polynomials And Factorials

An extremely roundabout way of doing it (if you have a lot of time and using a calculator/doing a bunch of multiplication sounds boring):

$9 \times 9 \times 9-9$

do some factoring:

$9((3 \times 3)^2-1)$

$(9)((3 \times 3)+1)(((3 \times 3)-1))$

$(9)(10)(8)$

$(3 \times 3) \times (2 \times 5) \times (2 \times 2 \times 2)$

which can be rearranged or multiplied out as

$1 \times 2 \times 3 \times 4 \times 5 \times 6$

By BODMAS, $n!=720$ or $n=6$