Armstrong Number Listing and checking if input is armstrong number or not

Current Armstrong-number check

An Armstrong number equals the sum of its digits raised to the number of digits. Use integer division when removing the right-most digit so the loop always works with integers.

<?php
$number = 153;
$original = $number;
$power = strlen((string) $number);
$sum = 0;

while ($number > 0) {
    $digit = $number % 10;
    $sum += $digit ** $power;
    $number = intdiv($number, 10);
}

echo $sum === $original ? 'Armstrong number' : 'Not an Armstrong number';
?>

What is an Armstrong number ?

A number equal to sum of the power of 3 of its digits. ( for 3 digit number )
A number equal to sum of the power of 4 of its digits. ( for 4 digit number )

A number equal to sum of the power of n of its digits. ( for n digit number )

Example 1:

153=1³ + 5³ + 3³
153=1 + 125 + 27
So 153 is an Armstrong number

Checking Armstrong numbers or generating Armstrong numbers in a range using PHP

Three digit Armstrong number

We can use pow() to get the cube of the digit. Inside the while loop we have taken out all digits of the number and then got the sum of the pow() value of each digit of the number. At the end if this, if sum is matching with the original number then we can print saying this is an Armstrong number.

$n1=153;
$n2=$n1;
$sum=0;
while($n1>0){
	$d=$n1%10; // reminder of the division
	$sum=$sum + pow($d,3);
	//$n1=floor($n1/10);
	$n1=intdiv($n1, 10);
	//$n1=intdiv($n1,10); // for PHP 7 and above
}
if($sum==$n2){
echo "$n2 is an Armstrong number "; 
}else{
echo "$n2 is NOT an Armstrong number "; 	
}

Output

153 is an Armstrong number

Armstrong numbers over a range

Armstrong number of any length can be collected by specifying a range. Here we will display all three digit, four digit and five digit Armstrong numbers. We will find out the length of the number ( in terms of number of digits ) and then use the same value to get the pow() of the digit.

for($i=10;$i<=100000;$i++){
$n2=$n1=$i;
$p=strlen($n1); // Number of digits in the number
$sum=0;
while($n1>0){
	$d=$n1%10; // reminder of the division
	$sum=$sum + pow($d,$p);
	//$n1=floor($n1/10);
	$n1=intdiv($n1, 10);
	//$n1=intdiv($n1,10); // for PHP 7 and above
}
if($sum==$n2){
echo "$n2 is an Armstrong number <br>"; 
}
}

Output is here

153 is an Armstrong number
370 is an Armstrong number
371 is an Armstrong number
407 is an Armstrong number
1634 is an Armstrong number
8208 is an Armstrong number
9474 is an Armstrong number
54748 is an Armstrong number
92727 is an Armstrong number
93084 is an Armstrong number

Introduction to PHP Factorial of a number Sum of Digits of a number
Strong number Fibonacci Series
Basic Codes Check the string or number is Palindrome or not in PHP

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

About the author Watch on YouTube

Connect:

Subscribe to our YouTube Channel here

Checking Armstrong number in PHP

Current Armstrong-number check

Example 1:

Three digit Armstrong number

Armstrong numbers over a range

Subhendu Mohapatra