1952. Three Divisors.txt

# 1952. Three Divisors

    Given an integer n, return true if n has exactly three positive divisors. Otherwise, return false.
    An integer m is a divisor of n if there exists an integer k such that n = k * m.

Constraints:

    1 <= n <= 10^4

Explanation:

    The problem asks us to find the numbers that have exactly three positive divisors.
    And only the numbers the are squares of prime numbers have exactly three positive divisors (1, itself, and it's square).
    Based on the above reason, what we need to do is to find the squares of prime numbers under 10000.
    So the answer will be:
        4, 9, 25, 49, 121, 169, 289, 361, 529, 841, 961, 1369, 1521, 1681, 1849, 2209, 2601, 2809, 3481, 3721, 4489, 5041, 5329, 6241, 6889, 7921, and 9409