Phrase guide
Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.
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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.
Definition source: English Wiktionary via Wiktextract
Topics: mathematics, sciences
Synonyms: none provided
Antonyms: sad number, unhappy number
History
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.
Across languages
1 source translations are retained for this English entry.
