January 2019 Fiendish Function

The Fiendish Function posed during January 2019 had the following sample guesses and replies:

  • GUESS
  • REPLY
  • 1
  • 1
  • 2
  • 2
  • 3
  • 6
  • 4
  • 42
  • 5
  • 21
  • 10
  • 88263

The rule was: "Take the factorial of the number, then reverse the order of the digits".

Suppose the guess was 11:

  • Find 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1, giving 39916800.
  • Reverse the order of the digits, giving 861993.

So the result is 861993.