Here's a possibly interesting prime puzzle. Call a prime $p$ flirtatious if the sum of its digits is also prime. Are there finitely many flirtatious primes, or infinitely many?
Flirtatious Primes
8
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elementary-number-theory
prime-numbers
puzzle
recreational-mathematics
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2@FredD$a$nielKline This is also a nice way for other mem$b$ers of the forum, such as myself, to come across an interesting problem they might otherwise not have heard about. – 2012-07-09