87

This number is a composite.

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87 is the largest number that yields a prime when any of the one-digit primes 2, 5 or 7 is inserted between any two digits. The only other such number is 27 (and trivially, the 1 digit numbers). [Hasler]

Submitted: 2018-05-21 11:08:44;   Last Modified: 2018-05-21 12:00:53.
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