This number is a prime.
The largest known "near-square" prime of the form (2^k - 1)^2 - 2 has index 253987. Discovered on May 7, 2007. [Emmanuel]
The largest known "near-square" prime of the form (2^k - 1)^2 - 2 has index 253987. Discovered on May 7, 2007. [Emmanuel]