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Armstrong Number Checker

Test if a number is an Armstrong number.

How it is calculated

An Armstrong (narcissistic) number equals the sum of its own digits, each raised to the power of the number of digits: n = d₁k + d₂k + … + dkk, where k is the digit count. The tool splits the number into digits, raises each to the power k, adds them, and reports the sum together with a yes or no verdict from comparing the sum with the original. Whole numbers from 0 to 1,000,000,000 are accepted; decimals are cut to the integer part. Every single-digit number qualifies, since d¹ = d.

Worked example

Test 153. It has k = 3 digits, so cube each: 1³ = 1, 5³ = 125, 3³ = 27. Add them: 1 + 125 + 27 = 153. The sum equals the original number, so 153 is an Armstrong number. Compare 154: 1 + 125 + 64 = 190, which differs, so it is not.

Try this example →

Common mistakes

  • Using a fixed power of 3 for every number; the power equals the digit count, so 1634 needs the 4th power.
  • Counting leading zeros as digits, such as writing 0153, which would make k = 4.
  • Expecting 10 to qualify because 1 + 0 = 1; the power is 2 here, giving 1, not 10.
  • Confusing Armstrong numbers with perfect numbers or palindromes; the property is about powers of digits.
  • Entering a value above one billion or a negative number, which returns no result.

About this calculator

This calculator checks whether a number is an Armstrong (narcissistic) number — one equal to the sum of its own digits each raised to the power of the digit count, such as 153 = 1³+5³+3³. Numbers like 9, 153, 9474, and 9926315 are famous examples across different digit lengths.

Programming students and puzzle enthusiasts use it to explore number theory concepts and test their own code — Armstrong number checks are a classic beginner programming exercise — against a reliable reference.

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Comments (1)

  • Editorial team

    A fun way to explore is to test numbers just after a known one. After 9926315, the next Armstrong numbers are the neighbouring pair 24678050 and 24678051, while 24678052 fails with a digit-power sum of 24,678,306. Seeing the sum beside the verdict helps you debug your own code for this classic exercise. Which language did you write your checker in, and did it agree with the tool?

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