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happy number

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happynumber (pluralhappy numbers)

1. (mathematics) Any number that eventually reaches 1 after some number ofiterations of replacing each of itsdigits by thesum of that digit'ssquares.

   Antonyms:sad number,unhappy number

   13 is ahappy number because 1² + 3² is 10, and 1² + 0² is 1.

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