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
The square of any prime number has exactly three factors: 22, 32, 52, etc.
By definition, a prime number has exactly two factors. So, there are no prime numbers with exactly three factors.
27
4, 9, 25
105
49 has exactly 3 factors (1, 7, and 49) and is greater than 40 and less than 60.
3*5*7*9 = 945 ...check if any number less than that has exactly four distinct factors.