Question

The number 9 has exactly three factors:

1, 3 and 9. Find the next number after 9 that has exactly three factors.

Answer 1

Numbers with 3 divider are squares of primes.

2^2 = 4. Div: 1, 2, 4;

3^3 = 9. Div: 1, 3, 9;

4^4 = 16. Div: 1, 4, 16;

5^5 = 25. Div: 1, 5, 25;

e.t.c.