25, 49, 121, 169
All numbers that are the square of primes have exactly 3 factors.
Numbers with exactly three factors are squares of prime numbers.
Squares of prime numbers have exactly three factors.
That's an infinite list.
The squares of all prime numbers above 2 have exactly 3 factors.
3, which can be divided by the odd numbers 1 and 3.
They are multiples of 3
Prime squares
900
3, 5 and 7
No.
2 and 3