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The number of 8digit primes (on a calculator) that remain prime if viewed upside down, in a mirror, or upside down in a mirror. [Russo] Mersenne wrongly thought 2^2571 is prime. In fact, 52 is the smallest base b for which (b^2571)/b1 is actually prime. 52! + 52 + 1 is prime. Note that 52 is the (52)rd untouchable number. [Mojdeh] The element with atomic number 52 (Tellurium) is the only one whose atomic weight's integer part is a Mersenne prime. [Wu] 52 = (5!*2!). [Firoozbakht]
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