609

This number is a composite.

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n = 609 = 5^2^2 - 2^2^2 is the (5^2)th natural number with the property p = n^2 + 2 is prime; additionally (p - 2^2, p) is a pair of prime cousins. Note that n^2 - (2*5) and n^2 + (2*5) are primes too! [Herault]