Harshad (Niven) Number Checker

How it is calculated

The tool writes the number as text, adds its decimal digits, and tests whether the number divides by that sum with no remainder: n mod S = 0, where n is the number and S is its digit sum. If it does, the answer is Yes and the quotient n ÷ S is shown; if not, the answer is No and the quotient shows a dash. For example 19 has digit sum 10, and 19 does not divide by 10, so it fails. Only positive whole numbers up to 10¹⁵ are accepted. Zero, negative numbers, decimals such as 12.5, numbers above 10¹⁵ and input with a thousands separator give no result. The test is done in base 10; a number can be a Harshad number in one base and not in another. Plain integer arithmetic is used, so large inputs are exact.

Common mistakes

• Dividing by the number of digits instead of their sum. For 2024 the divisor is 8 (the sum), not 4 (the count).
• Entering a number with a decimal part, a minus sign or a thousands separator. Only plain positive whole numbers work, and the tool shows nothing for 12.5, −18 or 2,024.
• Typing 0 as a trivial case. Zero is not accepted, because the digit sum would also be 0 and the division has no meaning.
• Reading the quotient dash as an error. A dash simply means the number is not a Harshad number, so there is no whole quotient.
• Assuming a number that fails here is a Harshad number in no number system. The check is in base 10 only.