The hepteicosillion is equal to \(10^{3\times 10^{81}+3}\) or \(10^{3\text{ sexvigintillion }3}\).[1] It is defined using Sbiis Saibian's generalization of Jonathan Bowers' -illion system.


Notation Lower bound Upper bound
Arrow notation \(1000\uparrow(1+10\uparrow81)\)
Down-arrow notation \(1000\downarrow\downarrow28\) \(503\downarrow\downarrow31\)
Steinhaus-Moser Notation 47[3][3] 48[3][3]
Copy notation 2[2[82]] 3[3[82]]
H* function H(H(26))
Taro's multivariable Ackermann function A(3,A(3,269)) A(3,A(3,270))
Pound-Star Notation #*((1))*(3,0,0,3,2)*6 #*((1))*(4,0,0,3,2)*6
BEAF {1000,1+{10,81}}
Hyper-E notation E(3+3E81)
Bashicu matrix system (0)(1)[16] (0)(1)[17]
Hyperfactorial array notation (58!)! (59!)!
Fast-growing hierarchy \(f_2(f_2(264))\) \(f_2(f_2(265))\)
Hardy hierarchy \(H_{\omega^22}(264)\) \(H_{\omega^22}(265)\)
Slow-growing hierarchy \(g_{\omega^{\omega^{\omega8+1}3+3}}(10)\)


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