The pentacthulhum (also called tethrarxihect[1]) is equal to E100#^^^#100 = E100#^^#^^#...#^^#^^#100 (100 #'s) in Extended Cascading-E Notation.[1] The term was coined by Sbiis Saibian.


The name of this number is based on the words "pentation" and "Cthulhu".

Approximations in other notations

Notation Approximation
BEAF \(\{X,X,1,2\}\ \&\ 100\) (weaker bound)

\(\{X,X,3\}\ \&\ 100 \) (stronger bound)

Bird's array notation \(\{100,100[1[1\neg3]2]2\}\)
Hyperfactorial array notation \(100![1(1)2]\)
Fast-growing hierarchy \(f_{\Gamma_{0}}(99)\)
Hardy hierarchy \(H_{\Gamma_{0}}(100)\)
Slow-growing hierarchy \(g_{\vartheta(\Omega_2)}(100)\)


  1. 1.0 1.1 Saibian, Sbiis. 4.3.9 - Extended Cascading-E Numbers Part III (9010 - 11870). Retrieved 2018-02-22.
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