50

This number is a composite.

The middle of only three integers n for which π(n x 2) = n/2. [Woods]

Expressible as the sum of primes in two distinct ways such that all primes involved are consecutive (beginning with 2): 50 = 2 + 5 + 7 + 17 + 19 = 3 + 11 + 13 + 23. [Rivera]

50 is the smallest number m such that sum of each digits of prime(m) raised to m is prime. I.e., prime(50) = 229; 2^50 + 2^50 + 9^50 is prime. [Kazemi]

There are 50 primes of the form 4n+3 up to 4n+3 = 500. [Post]