n and r integers, 0 ≤ r ≤ n, n capped at 170 for safety.
Permutation count P(n,r) = n×(n−1)×…×(n−r+1) for integers with 0 ≤ r ≤ n and n ≤ 170 to reduce overflow risk. P(n,0)=1. Output is shown as a decimal string from big integers.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.