Factorial trailing digits 2 (noch nicht übersetzt)

For any N, let f(N) be the last twelve hexadecimal digits before the trailing zeroes in N!.

For example, the hexadecimal representation of 20! is 21C3677C82B40000,
so f(20) is the digit sequence 21C3677C82B4.

Find f(20!). Give your answer as twelve hexadecimal digits, using uppercase for the digits A to F.