I believe here are 51 such numbers.
Ffgh
none.
Expressed in digits, this is equal to 14,500,000.
Two (or four) digits added together cannot equal 42. Two-digit numbers multiplied together cannot equal 82.
3721
21.
none.
Expressed in digits, this is equal to 14,500,000.
Two (or four) digits added together cannot equal 42. Two-digit numbers multiplied together cannot equal 82.
07, 70, 16, 61, 25, 52, 34, 43: 8 numbers
3721
21.
There are 17 such numbers.
50
21
There are 15 of them.
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.
16 of them.