I assume you mean "a faster way". Calculating values of n! for values of n seems to me tobethe "direct" way! I presume you know that 6!= 6(5)(4)(3)(2)= 120(6)= 720 so 7!= 7(6!)= 7(720).

As forreally bignumbers (1000 is NOT "really big"!), you can get anapproximatesolution by using Strirlings formula: n! is approximately equal to .