The divisors of 40 are: 1, 2, 4, 5, 8, 10, 20, 40.
The divisors of 40: 1 | 2 | 4 | 5 | 8 | 10 | 20 | 40 (8 divisors)
The divisors of 80 are: 1, 2, 4, 5, 8, 10, 16, 20, 40, 80.
36
80 has 10 divisors: 1, 2, 4, 5, 8, 10, 16, 20, 40, 80.
200 has 12 divisors: 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 200.
none
400's divisors are 1, 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, 80, 100, 200, 400.
The divisors of 280 are: 1, 2, 4, 5, 7, 8, 10, 14, 20, 28, 35, 40, 56, 70, 140, 280.
400 has 15 divisors: 1, 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, 80, 100, 200, 400.
The divisors of 800 are: 1, 2, 4, 5, 8, 10, 16, 20, 25, 32, 40, 50, 80, 100, 160, 200, 400, 800.
28 is such a number.