Armstrong Number

An Armstrong number is the one whose value is equal to the sum of the cubes of its digits.

0, 1, 153, 371, 407, 471, etc are Armstrong numbers.

For example,

  1. 407 = (4*4*4) + (0*0*0) + (7*7*7)
  2.         = 64 + 0 + 343
  3. 407 = 407

Logic:

  • Take the number.
  • Store it in a variable.
  • Take a variable for sum.
  • Divide the number with 10 until quotient is 0.
  • Cube the remainder.
  • Compare sum variable and number variable.

Armstrong number in PHP

Below program checks whether 407 is Armstrong or not.

Example:

  1. <?php
  2. $num=407;
  3. $total=0;
  4. $x=$num;
  5. while($x!=0)
  6. {
  7. $rem=$x%10;
  8. $total=$total+$rem*$rem*$rem;
  9. $x=$x/10;
  10. }
  11. if($num==$total)
  12. {
  13. echo “Yes it is an Armstrong number”;
  14. }
  15. else
  16. {
  17. echo “No it is not an armstrong number”;
  18. }
  19. ?>

Output:

PHP Armstrong number 1

Look at the above snapshot, the output displays that 407 is an Armstrong number.


Armstrong number using Form in PHP

A number is Armstrong or can also be checked using a form.

Example:

  1. <html>
  2. <body>
  3.  <form method=“post”>
  4.  Enter the Number:
  5.    <input type=“number” name=“number”>
  6.    <input type=“submit” value=“Submit”>
  7.   </form>
  8. </body>
  9. </html>
  10. <?php
  11.  if($_POST)
  12.  {
  13.   //get the number entered
  14.   $number = $_POST[‘number’];
  15.   //store entered number in a variable
  16.   $a = $number;
  17.   $sum  = 0;
  18.   //run loop till the quotient is 0
  19.   while$a != 0 )
  20.   {
  21.    $rem   = $a % 10; //find reminder
  22.    $sum   = $sum + ( $rem * $rem * $rem ); //cube the reminder and add it to the sum variable till the loop ends
  23.    $a   = $a / 10; //find quotient. if 0 then loop again
  24.   }
  25.   //if the entered number and $sum value matches then it is an armstrong number
  26.   if$number == $sum )
  27.   {
  28.    echo “Yes $number an Armstrong Number”;
  29.   }else
  30.   {
  31.    echo “$number is not an Armstrong Number”;
  32.   }
  33.  }
  34. ?>

Output:

On entering the number 371, we got the following output.

On entering the number 9999, we got the following output.

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