happy number
happy number noun: any number that eventually reaches 1 after some number of iterations of replacing each of its digits by the sum of that digit's squares.
Noun
happy number (plural happy numbers)
- Any number that eventually reaches 1 after some number of iterations of replacing each of its digits by the sum of that digit's squares.
- 13 is a happy number because 1² + 3² is 10, and 1² + 0² is 1.
- Antonyms:
- sad number, unhappy number
Antonyms of happy number
Forms of happy number
| plural | happy numbers |
|---|
Origin of happy number
Popularised by the British mathematician Reginald Allenby in the 1960s, who developed this concept from his daughter, while similar mathematical formulas may have existed earlier in Russia. The number was called "happy" because the iteration to reach 1 was treated like a game of numbers, where reaching 1 is compared to "winning" that game.
Questions about happy number
- What does happy number mean?
- Happy number means any number that eventually reaches 1 after some number of iterations of replacing each of its digits by the sum of that digit's squares.
- What part of speech is happy number?
- Happy number is a noun.
- What is the plural of happy number?
- The plural of happy number is happy numbers.
Words near happy number in the dictionary
Source and license
Adapted from Wiktionary: happy number (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.
Last updated:
Cite this entry: “happy number.” Word.ws, https://word.ws/happy_number. Based on Wiktionary, CC BY-SA 4.0.