30, 42, 66, 70 and 78.
By definition, a prime number has exactly two factors. So, there are no prime numbers with exactly three factors.
They all are prime numbers except 1
As a product of its prime factors: 5*17*23 = 1955
Here are all the prime numbers less than 12: 2, 3, 5, 7, 11
4, 9, 25, and 49
42 and its next three multiples.
Prime numbers
The set of prime factors of the numbers from 1 to 15,000 would be the set of prime numbers between 1 and 15,000. The link below has a list of the first 10,000 prime numbers, so if you take the primes less than 15,000, you will have the set of prime factors of the first 15,000 numbers. For prime factors of individual numbers, check the related question, "What are the prime factors of the numbers from 1 to 200?" Also check for WikiAnswers questions in the form of "What are the prime factors of __?" and "What are the factors and prime factors of __?"
The sum of the three greatest prime numbers that are less than 39 is 97.
30 (2 x 3 x 5) and 42 (2 x 3 x 7) are the only numbers less than 60 having three different prime factors.
Prime squares have three factors. There are 11 of them in that range.
Numbers with exactly 6 factors are perfect squares of prime numbers. The prime factorization of a number with exactly 6 factors is in the form ( p^2 ), where ( p ) is a prime number. There are 10 prime numbers less than 30: 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29. So, there are 10 numbers less than 30 that have exactly 6 factors.