They are numbers that are the product of two different prime numbers.
If the primes are p and q, the four factors are 1, p, q and pq.
Numbers with exactly three factors are squares of prime numbers.
All numbers that are the square of primes have exactly 3 factors.
4, 9 and 25.
Numbers with three factors are squares of primes. So: 4, 9, 25
Factors
8 10 12 and 13
4 and 9
Squares of prime numbers have exactly three factors.
Numbers with exactly three factors are squares of prime numbers.
All numbers that are the square of primes have exactly 3 factors.
2 4 6
6, 8 and 10, among others.
4, 9 and 25.
Squares of prime numbers, like 4, 9 and 25.
All numbers that have exactly two factors are prime numbers whereas composite numbers have more than two factors.
4 (factors 1, 2 and 4) and 9 (factors 1, 3 and 9) are two examples.
Numbers with three factors are squares of primes. So: 4, 9, 25