5678 is only one 4-digit number.
If you're willing to move the digits around to
different positions, you can make 23 more.
23
-5674
Six - assuming 0123 does not count ... 1234 2345 3456 4567 5678 6789
There are 16 4-digit numbers that can be made up from 9 and 6.
49765
The first digit can have 5 possible numbers, the second digit can have 4, the third 3, the fourth 2. 5
-5674
24
Six - assuming 0123 does not count ... 1234 2345 3456 4567 5678 6789
5678 \
17
3 digit numbers are lessthan 4 digit numbers
There are 2941 4-digit numbers such no two of its digits differ by 1.
The number 1234567890 can create about 39 of 40 4 digit numbers.
There are 16 4-digit numbers that can be made up from 9 and 6.
-2
12 numbers
There are 90 such numbers.