99
21.
Three of them.
1
There are no 3-digit whole numbers whose digits sum to 3. The smallest 3-digit number is 100, and the largest is 999, but in neither case is the sum of the digits equal to 3.
27
1348.
412
002+002+001=005
There are 5460 five digit numbers with a digit sum of 22.
The sum of the individual digit is itself
1,111,111 since 17 = 1
55 52+52 = 50