0 123 456
OR if you don't want to count the zero:
1 234 567
1,234,567
The smallest 4-digit number without any repeated digits is 1023, as it starts with the smallest possible digit (1) followed by the next smallest digits (0, 2, 3). The largest 4-digit number without any repeated digits is 9876, which uses the largest digits available in descending order.
none
123456.
1023456789
1,234,567
none
102
123456.
1023456789
1234567
102345
5
Since there are only five different digits, a 6-digit number can only be generated if a digit can be repeated. If digits can be repeated, the smallest 6-digit number is 111111.
5
10234567
0123456789