9x9x8x7x6x5x4x3
=1632960
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
There are 7,290 different 4-digit numbers that can be formed from the digits 1-9 without repetition.
1
36