Hollom's number, named after its inventor Lawrence Hollom, is equal to Ia(200) using the iota function, where a is the number of Planck times in \(1.17866 \times 10^{54}\) years (about \(6.895 \times 10^{104}\)).[1] It is a thought experiment like the function used to define it, and it is not a well-defined number.
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Busy beaver numbers (based on Turing theories): \(\Sigma(1919)\) (1919th busy beaver number) · Fish number 4 · \(\Xi(10^6)\) · \(\Sigma_{\infty}(10^9)\)
Rayo's numbers (based on Set theories): Rayo's number (Rayo(10100)) · Fish number 7 · BIG FOOT (FOOT10(10100)) · Little Bigeddon · Sasquatch · Large Number Garden Number
Miscellany: Hollom's number · Oblivion · Utter Oblivion · (Ultimate Oblivion)