Peterson Number in Java

In this section, we will learn what is Peterson number and how can we check whether a given number is Peterson or not through a Java program.

Peterson Number

A number is said to be Peterson if the sum of factorials of each digit is equal to the sum of the number itself.

Steps to Find Peterson Number

Read or initialize a number (n).
Find the last digit (d) of the given number.
Find the factorial (fact) of the digit.
Add the factorial (fact) to a variable
Repeat steps 2 to 4 until the given number becomes 0.
Compare the sum with n. If both are equal, the given number is Peterson, else not.

Example of Peterson Number

Suppose, we have to check the number (n) 145 is Peterson or not.

Number = 145

145 = !1 + !4 + !5

=1+4*3*2*1+5*4*3*2*1

=1+24+120

145=145

We observe that the number and the sum of factorials of digits are equal to the number itself. Hence, 145 is a Peterson number.

Peterson Number Java Program

In the following program, we have taken an array of factorial to quickly find the factorial. You can use the logic also.

PetersonNumberExample.java

import java.io.*; import java.util.*; public class PetersonNumberExample1 { //an array is defined for the quickly find the factorial static long[] factorial = new int[] { 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600}; //driver code public static void main(String args[]) { //constructor of the Scanner class Scanner sc = new Scanner(System.in); System.out.print("Enter a number to check: "); //reading a number from the user int n=sc.nextInt(); //calling the user-defined function to check Peterson number if (isPeterson(n)) System.out.println("The given number is a Peterson number."); else System.out.println("The given number is not a Peterson number."); } //function to check the given number is Peterson or not static boolean isPeterson(int n) { int num = n; int sum = 0; //loop executes until the condition becomes false while (n > 0) { //determines the last digit of the given number int digit = n % 10; //determines the factorial of the digit and add it to the variable sum sum += factorial[digit]; //removes the last digit of the given number n = n / 10; } //compares sum with num if they are equal returns the number itself return (sum == num); } }

Output 1:

Enter a number to check: 145
The given number is a Peterson number.

Output 2:

Enter a number to check: 773
The given number is not a Peterson number.

Peterson Number in Java

Peterson Number

Steps to Find Peterson Number

Example of Peterson Number

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Peterson Number Java Program

Java Number Programs

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