All of them. That is, 1,000 of them (including zero).
012345
81
823543
94205 if digits are not to be repeated and 99999 if digits can be repeated
500
012345 or -543210, if negative numbers are permitted.
99876
012345
543210
81
823543
There are 5! = 120 such numbers.
94205 if digits are not to be repeated and 99999 if digits can be repeated
738 numbers
27 if the digits can be repeated. 6 if not.
3x3x3=27
24