Question

please show the code in java，thanks

5. Perfect Numbers Version 2: Write a program which computes perfect numbers according the following algorithm: for each prime, p: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53 if 2P 1 s prime (2P (2 is perfect: print both p and (2P 1)(2) Note: You will need to use the Biglnteger clas for thist

Answer 1

package abc;

import java.util.Scanner;
import java.lang.Math;
import java.math.BigInteger;

public class Perfect {
public static void main(String args[]) {
   Scanner in=new Scanner(System.in);
   System.out.println("Enter the number:");
BigInteger n=in.nextBigInteger();
if(prime(n.intValue())) {

double ans=Math.pow(2.0,n.doubleValue());
ans=ans-1;

double p1=Math.pow(2,(n.intValue()-1));

if(prime(ans)) {
   System.out.println("Prime number is :"+n+" , perfect number is : "+(ans*p1));
}else {
   System.out.println("No perfect number found!");
}
}else {
   System.out.println("Entered number is not prime!");
}
}
public static boolean prime(double m) {
   int count=0;
   for(double i=2;i<m;i++) {
       if(m%i==0) {
           count++;
       }
   }
   if(count==0) {
       return true;
   }
   return false;
}
}

output:

Enter the number:
3
ans = 7.0
p1 = 4.0
Prime number is :3 , perfect number is : 28.0