If you'll accept a decimal, then it's .0123456789
If you want whole numbers only, and you'll accept a leading zero, then it's 0,123,456,789.
If not, then it's 1,023,456,789.
1,234,567
5
none
5
0132 or 1234 0123 or without 0 at front = 1023
The smallest number with no digits repeated would either be zero or one, depending on the set of numbers you want to choose from.
0123456789
102
10234567
1023456789
123456.
1023456789