56863...18433 (54-digits)

This number is a prime.

                 5686 3064753535 6955169033 4109408678 0483936074 2060818433

On March 27, 2010, Michael Vang found a 54-digit factor of F₁₂ using GMP-ECM. F₁₂ is the 12th Fermat number 2^(2^12) + 1 = 2^4096 + 1.