Fzeighteen

Fzeighteen is equal to \(18^{18}\) = \(18\uparrow\uparrow2\) = 39,346,408,075,296,537,575,424.

Etymology
Fzeighteen is made out of the Fz- prefix and eighteen, which ends up becoming \(18^{18}\) when concatenated backwards, or 18 to the power of itself.