Fzfifty

Fzfifty is equal to \(50^{50}\) = \(50\uparrow\uparrow2\) = 8,881,784,197,001,252,323,389,053,344,726,562,500,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

Etymology
Fzsixteen is made out of the Fz- prefix and fifty, which ends up becoming \(50^{50}\) when concatenated backwards, ergo, 50 to the power of itself.