This number is a composite.

+ The number of 8-digit primes (on a calculator) that remain prime if viewed upside down, in a mirror, or upside down in a mirror. [Russo]

+ Mersenne wrongly thought 2^257-1 is prime. In fact, 52 is the smallest base b for which (b^257-1)/b-1 is actually prime.

+ 52! + 52 + 1 is prime. Note that 52 is the (5-2)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 = π(5!*2!). [Firoozbakht]

(There are 5 curios for this number that have not yet been approved by an editor.)

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