Frequently Asked Java Program 28: Java Program to Find if Given Number Is a Perfect Number

A Perfect number is a positive integer that is equal to the sum of its proper divisors excluding the number itself.

For Example: Take Number 6. Its divisors are 1, 2 , 3 and 6. When we add all divisors except 6 ( as it is number itself) (i.e. 1+2+3= 6), it is equal to actual number. So we can say Number 6 is a perfect number.

The smallest perfect number is 6. Other perfect numbers are 28, 496, and 8,128.

Logic:

1. When we divide a number say X by other number say Y and reminder is zero, then number Y is a proper divisor. All proper divisor of a number X are between 1 and X/2. ( 1 and X/2 are included) . To find the proper divisor we need to divide the number by 1 to number/2.
2. We need to keep adding all divisors.

Java Program:

package StringPrograms;

import java.util.Scanner;

public class PerfectNumber {
        
        
        
        
        public static void perfectNumber(int userInput)
        {
                // Handling numbers less than or equal to zero
                if(userInput