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Java-based LeetCode algorithm problem solutions, regularly updated
507\. Perfect Number
Easy
A [**perfect number**](https://en.wikipedia.org/wiki/Perfect_number) is a **positive integer** that is equal to the sum of its **positive divisors**, excluding the number itself. A **divisor** of an integer `x` is an integer that can divide `x` evenly.
Given an integer `n`, return `true` _if_ `n` _is a perfect number, otherwise return_ `false`.
**Example 1:**
**Input:** num = 28
**Output:** true
**Explanation:** 28 = 1 + 2 + 4 + 7 + 14 1, 2, 4, 7, and 14 are all divisors of 28.
**Example 2:**
**Input:** num = 7
**Output:** false
**Constraints:**
* 1 <= num <= 108