It is ... wait for it ... NINE!
There are 5460 five digit numbers with a digit sum of 22.
Nine hundred thirty (930) is the highest three digit number whose digits have a sum of 12. 9+3+0=12. Any numbers higher than that will give you an sum greater than 12.
35.
21.
There are nine of them. They are:108117126135144153162171180
900 It is the only three digit number with a nine in the numbers place
It is ... wait for it ... NINE!
9, 27, 45, 63, 81 Five of them.
-8
None. The sum of one digit can't be twice the size of the digit.
120
There are 5460 five digit numbers with a digit sum of 22.
Only one . . . 999 .
There are five such numbers.
-3
1010111 1111100 1011101 and many more