N-factorial n actual factrl(n) 1 1 1 2 2 2 3 6 6 4 24 24 5 120 120 6 720 720 7 5040 5040 8 40320 40320 9 362880 362880 10 3628800 3628800 11 39916800 39916800 12 479001600 479001600 13 6227020800 6227020800 14 8.717829e+10 8.717829e+10 15 1.307675e+12 1.307674e+12 20 2.432904e+18 2.432902e+18 25 1.551122e+25 1.551121e+25 30 2.652528e+32 2.652529e+32