Select 1 unique numbers from 18 to 21
Total possible combinations (ways)
If order does not matter (e.g. most lottery numbers): 4
If order matters (e.g. pick3 numbers, permutations, lock combinations, pin-codes): 4
If order does not matter (e.g. most lottery numbers): 4
If order matters (e.g. pick3 numbers, permutations, lock combinations, pin-codes): 4