Leetcode perfect number simple

title ：507 Perfect number - Simple

subject

For one Positive integer , If it and all but itself Positive factor The sum is equal , Let's call it alpha 「 Perfect number 」.

Given a Integers n, If it's a perfect number , return true, Otherwise return to false

Example 1

 Input ：num = 28
 Output ：true
 explain ：28 = 1 + 2 + 4 + 7 + 14
1, 2, 4, 7,  and  14  yes  28  All positive factors of .

Example 2

 Input ：num = 6
 Output ：true

Example 3

 Input ：num = 496
 Output ：true

Example 4

 Input ：num = 8128
 Output ：true

Example 5

 Input ：num = 2
 Output ：false

Tips

• 1 <= num <= 108

Code Java

public boolean checkPerfectNumber(int num) {
    
    if (num == 1) return false;
    int sum = 1;
    for (int i = 2; i < Math.sqrt(num); i++) {
    
        if (num % i == 0)
            sum += i + num / i;
    }
    if (sum == num)
        return true;
    return false;
}