Armstrong Number Checker – Narcissistic Test

An Armstrong (narcissistic) number equals the sum of its own digits each raised to the power of the digit count. For 3-digit numbers the power is 3: 153 → 1³+5³+3³ = 1+125+27 = 153 ✓, and its siblings 370, 371 and 407 complete the three-digit club. For 4-digit numbers the power is 4: 1634 → 1+1296+81+256 = 1634 ✓. The checker prints the digit-by-digit powers, their sum, and the verdict; single digits 1–9 are all trivially Armstrong (k = 1). The sequence is finite per digit-length and known to end at 39 digits (the largest is 115132219018763992565095597973971522401). Related curiosities appear too: 371 is also the sum of cubes of its digits, and 5 → 5¹ works but 10 → 1¹+0¹ = 1 fails.

1. 1

   Enter a number

   Any positive integer such as 153

2. 2

   Count the digits

   The exponent k equals the digit count (3 for 153)

3. 3

   Raise and sum

   Each digitᵏ is computed and listed: 1, 125, 27

4. 4

   Compare with the original

   Sum 153 equals the input → Armstrong

• 1

  The exponent is the digit count — 153 uses cubes, 1634 fourth powers

• 2

  All single digits 1–9 are Armstrong numbers

• 3

  370, 371 and 407 join 153 as the only 3-digit cases

• Raising digits to a fixed power 3 regardless of digit count

• Including 0 — it has one digit and 0¹ = 0, conventionally excluded

• Summing the digits first and then raising the sum

• Expecting many hits: only four exist below 10,000