Fzeighty

Fzeighty is equal to \(80^{80}\) = \(80\uparrow\uparrow2\) ≈ \(1.76685\times10^{152}\).

Full decimal expansion:

176684706477838432958329750074291851582748389687561895812160620129261977600000000000000000000000000000000000000000000000000000000000000000000000000000000

Etymology
Fzeighty is made out of the Fz- prefix and eighty, which ends up becoming \(80^{80}\) when concatenated backwards, or 80 to the power of itself.