Chapter 4, Problem 21E

Explanation of Solution

Program:

//define the static function

public static void perfectNumbers(int n) {

    //print statement

    System.out.print("Perfect numbers up to " + n + ":");

    //loop initialized to determine the sum value

    for (int current = 1; current <= n; current++) {

        //declare and initialize the variable

        int sum = 0;

        //loop initialized to determine the sum value

        for (int factor = 1; factor < current; factor++) {

            //condition initialized to check whether input is divisible by the factor

            if (current % factor == 0) {

                //evaluate the value

                sum = sum + factor;

           ;&#x...