That depends entirely on the number of digits each number is permitted to have !
there are 63 combos
5
By making a number tree that could have as many as 1,000,000 combos.
9,999 different combos well 10,00 if you add 0 in with it
120, if you use each number once.
2 Father son combos, The Bushs and The Adams
94
There are 3,628,800 different permutations that can be made when using the numbers 0 through 9, if each number is only used once in each combination.
15
10,000
2304
It is: 9C7 = 36