It is 30.
30
30
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 smallest number that has exactly three factors is 4.
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.
4, 9, 25
105
27
98
49 has exactly 3 factors (1, 7, and 49) and is greater than 40 and less than 60.