It is 30.
30
The smallest number that has exactly three factors is 4.
It's a multiple of 5, a multiple of 6 (since it's between twin primes), and less than 50. The only possibility is 30. To check: The factors of 30 are 1, 2, 3, 5, 6, 10, 15, and 30
The only number less than 100 with exactly nine factors is 36. 19 is not one of the factors.
16
95
24
By definition, a prime number has exactly two factors. So, there are no prime numbers with exactly three factors.
The square of any prime number has exactly three factors: 22, 32, 52, etc.
49
49