102345. We can't start with 0 because that would make it a 5 digit number. Start with "1" because it is the next smallest, then use the 0 because it will reduce the number the most when in the tens of thousands digit. Then use the smallest from there on, giving us 2,3,4,5.
1111111111
It is 10000.If you meant ONLY 2 digits alike, then it is 10023.
10123456789
1,111,111,111
4
10,023,456,789
10,023,456,789
-9876543 or, if only positive number are permitted, 1023456.
The largest digits number with only 2 digits alike is 99
9876543210
987654321 is the highest nine-digit number with no repeated digits.
98,765