7

This number is a prime.

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The first prime happy number. Replace a number by the sum of the squares of its digits, and repeat the process until the number equals 1, or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are called happy numbers. There are exactly 7 prime happy numbers less than 100. Can you find all 7?

Submitted: 1999-09-02 23:40:00; Last Modified: 2009-03-29 17:48:48.