This program is used to check whether a given number is a perfect number or not. So what is a Perfect Number? A perfect number is any integer that equals the sum of its divisors(including 1 and excluding the number itself). For example, consider the number 6. The divisors of 6 are 1,2,3,6. Excluding the number itself i.e, 6, the sum of other divisors is equal to 6 (1+2+3 = 6). Hence 6 is a perfect number.

### Java Program to find if a Number is Perfect or not

import java.io.*; import java.util.*; class perfect { public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); System.out.print("\nEnter a number:"); int n = Integer.parseInt(br.readLine()); int sum = 0; for(int i=1;i<n;i++) { if(n%i==0) { sum = sum + i; } } if(sum == n) System.out.println("\nGiven number is a perfect number"); else System.out.println("\nGiven number is not perfect number"); } }

### Java Program to find list of Perfect Numbers in a Given range

//Java program to display perfect numbers in a given range import java.io.*; class perfect_list { public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); System.out.print("\nEnter the range:"); long range = Long.parseLong(br.readLine()); System.out.println("\nThe perfect numbers between 1 and "+range+" are:"); for(int i=1;i<range;i++) { int sum = 0; { for(int j=1;j<i;j++) { if(i%j == 0) { sum = sum + j; } } if(sum == i) { System.out.println(i); } } } } }

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