Googology Wiki
Googology Wiki

The googolseptiplex, googolheptaplex, or googolplexplexplexplexplexplexplex is equal to E100#8 = EEEEEEEE100 in Hyper-E Notation.[1]

It is also equal to \(^{9}10^{2}\) = 1010101010101010100, or one followed by a googolsextiplex (googolplexplexplexplexplexplex) zeros. It is 10101010101010100+1 digits long.

Writing down the full decimal expansion would take 10101010101010100-6 books of 400 pages each, with 2,500 digits on each page (except for the first, which would have 2,501).


The name of this number is based on Latin prefix "septi-" and the number "googolplex"

Approximations in other notations

Notation Approximation
Up-arrow notation \(57 \uparrow \uparrow 9\)
Chained arrow notation \(57 \rightarrow 9 \rightarrow 2 \)
Notation Array Notation \((57\{2,2\}9)\)
Hyper-E notation \(\textrm{E}100\#8\) (exact)
Hyperfactorial array notation \(12!1\)
BEAF \(\{57,9,2\}\)
Bird’s array notation \(\{57,9,2\}\)
Fast-growing hierarchy \(f^8_2(326)\)
Hardy hierarchy \(H_{\omega^28}(324)\)
Slow-growing hierarchy \(g_{\varepsilon_0}(9)\)


  1. Saibian, Sbiis. Hyper-E Numbers

See also