0,1,2,3,4,5,6,7,8 and 9 1 way to pick the 1st digit (as 0). 9 ways to pick the 2nd digit. 8 ways to pick the 3rd digit. 7 ways to pick the 4th digit. 6 ways to pick the 5th digit. 5 ways to pick the 6th digit. 4 ways to pick the 7th digit. 3 ways to pick the 8th digit. 1×9×8×7×6×5×4×3 = 9!/2! = 181440 Edwin