<p>Given an integer <code>n</code>, return <code>true</code><em> if </em><code>n</code><em> has <strong>exactly three positive divisors</strong>. Otherwise, return </em><code>false</code>.</p> <p>An integer <code>m</code> is a <strong>divisor</strong> of <code>n</code> if there exists an integer <code>k</code> such that <code>n = k * m</code>.</p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> n = 2 <strong>Output:</strong> false <strong>Explantion:</strong> 2 has only two divisors: 1 and 2. </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> n = 4 <strong>Output:</strong> true <strong>Explantion:</strong> 4 has three divisors: 1, 2, and 4. </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= n <= 10<sup>4</sup></code></li> </ul>