Suppose you sample randomly, without replacement, a number between 1 and 999999, all outcomes have the same probability of being selected.What is the probability that the digits of the number selected add up to 23

None under 100 will = 23

995 = 9 + 9 + 5 = 23
599 = 9 + 9 + 5 = 23
959 = 9 + 9 + 5 = 23
869
779
788

Do you have a formula you can use? I don't.