Javascript Algorithm:Perfect Number

A 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

Solution:

let num = 8128;

var checkPerfectNumber = function (num) {

let sum = 1;

let max = Math.sqrt(num);

let isOdd = num % 2;

// divisors of 1 other than itself is none so its not perect number

if (num == 1) {

return false;

}

let i = 2;

while (i < max) {

if (num % i == 0) {

sum += i;

sum += num / i;

}

if (isOdd == 1) {

i += 2;

} else {

i++;

}

}

return sum === num;

};

let isPerfect = checkPerfectNumber(num);

console.log(`${num} is perfect number:${isPerfect}`);

Output:

8128 is perfect number:true