55, 65
Any number with five factors is composite. There isn't one in that range.
16
77 is one possibility.
A prime number
Each prime number has only two factors which are itself and one.
The only number less than 100 with exactly nine factors is 36. 19 is not one of the factors.
A prime number !
A positive integer with only two factors: one and the number itself.
16
1 is the only number that has exactly one factor. A prime number has exactly two factors, 1 and the number itself. A composite number has more than two factors.
The proper factors are the regular factors without one and the number itself.