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.
012345
99876
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
3x3x3=27
500
24