763920
757
24
500
There are 5*4*3 = 60 such numbers.
With repeated digits, 43 = 64 Without repeated digits, 4*3*2 = 24
1 set
The answer will depend on how many digits you have at your disposal. Working with the 10 digits, and barring leading zeros, there are 8,877,690 numbers.
162
1
36
6*6*3 = 108 numbers.