Narcissistic Number in Java

In this section, we will learn what is a narcissistic number and also create Java programs to check if the given number is a narcissistic number or not. The narcissistic number program is frequently asked in Java coding interviews and academics.

Narcissistic Number

A narcissistic number is a number that is the sum of digits, each raised to the power of the number of digits in the given number. In other words, it is m-digit positive numbers equal to the sum of the m-th powers of their digits. It is also known as pluperfect, or Plus Perfect, or Armstrong number. It is an OEIS sequence A005188.

Let's understand the narcissistic number with examples.

Narcissistic Number Examples

Consider the following numbers.

153 = 1³ + 5³ + 3³ = 1 + 125 +27 = 153

8208 = 8⁴ + 2⁴ + 0⁴ + 8⁴ = 4096 + 16 + 0 + 4096 = 8208

4210818 = 4⁷ + 2⁷ + 1⁷+ 0⁷ + 8⁷ + 1⁷ + 8⁷ = 16384 + 128 + 1 + 0 + 2097152 + 1 + 2097152 = 4210818

We see that the total numbers of digits in the given number are the power and the sum of the powers of each digit is the same number that we have considered. Hence, the given numbers are narcissistic numbers

First few narcissistic numbers are 1, 2, 3, 4, 5, 6, 7, 8, 9, 153, 370, 371, 407, 1634, 8208, 9474, 54748, 92727, 93084, 548834, 1741725, 4210818, 9800817, 9926315, 24678050, 24678051, 88593477, 146511208, 472335975, 534494836, 912985153, 4679307774, 32164049650, 32164049651, 4338281769391370, 3706907995955475988644380, 19008174136254279995012734740, 186709961001538790100634132976990, and 115132219018763992565095597973971522400.

Steps to Find Narcissistic Number

Read or initialize a number N.
Count the number of digits of the given number N and store it in a variable power.
Find the power of each digit and add the result in a variable sum.
Compare the variable sum with the given number N. If both are equal, the given number is a narcissistic number, else not.

Let's implement the above steps in a Java program.

Narcissistic Number Java Program

NarcissisticNumberExample1.java

import java.util.*;
import static java.lang.Math.*;
public class NarcissisticNumberExample1
{
//function counts the number of digits 
int countDigits(int number)
{
if (number == 0)
return 0;
return 1 + countDigits(number / 10);
}
//function checks if the given number is a Narcissistic number or not
boolean isNarcissistic(int number)
{
//count the number of digits
int pwr = countDigits(number);
//assigning the value of n in the variable n
int n = number;
//stores the sum 
int sum = 0;
//loop executes until the condition becomes false
while(n > 0)
{
//first it finds the last digit of the given number
//then it calculates the power of the last digit
//at last the result is added to the variable sum
sum+= pow(n % 10, pwr);
//removes the last digit from the given number
n = n / 10;
}
//compares the sum with number
return (number == sum);
}
//driver code
public static void main(String args[])
{
NarcissisticNumberExample1 nrstic = new NarcissisticNumberExample1 ();
Scanner sc = new Scanner(System.in);
System.out.print("Enter the number: ");
//reads an integer from the user
int number = sc.nextInt();
//
if (nrstic.isNarcissistic(number))
System.out.println("The given number "+number+" is a narcissistic number.");
else
System.out.println("The given number "+number+" is not a narcissistic number.");
}
}

Output 1:

Enter the number: 93084
The given number 93084 is a narcissistic number.

Output 2:

Enter the number: 57357
The given number 57357 is not a narcissistic number.

Let's find all the narcissistic numbers between a given range 1 to 1000.

NarcissisticNumberExample2.java

import java.util.LinkedList;
public class NarcissisticNumberExample2
{
public static void main(String args[])
{
for (int i = 1; i < 1000; i++) 
{
int n = i;
//creates a LinkedList
LinkedList<Integer> data = new LinkedList<>();
//the loop executes until the number becomes 0
while (n > 0) 
{
//adds the last digit of the given number in the List    
data.push( n % 10 );
//removes the last digit from the number
n = n / 10;
}
//stores the sum
int sum = 0;
//loop iterates over the List
for(Integer num : data) 
{
//finds the power of the digit and add the result to the variable sum    
sum += Math.pow(num, data.size());
}
//compares the sum with the given number 
if(i == sum) 
{
//prints all the Narcissistic number in a given range 
System.out.println(i);
}
}
}
} 

Output: