6
the numbers that can go into 28 are 1,2,4,7,14 and 28.
Infinity.
There are infinitely many such numbers.
6 of them go in evenly.
To make whole numbers. The numbers 1,2,4,17,34,68. So 6 numbers.
Four.
6
1,3,5,7,15,35,105
21
Two of them.
1,2,4,7,8,14,28,56