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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).

## Etymology

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 $$\{57,9,2\}$$
Fast-growing hierarchy $$f_3(9)$$
Hardy hierarchy $$H_{\omega^28}(324)$$
Slow-growing hierarchy $$g_{\varepsilon_0}(9)$$

## Pronunciation

It is likely pronounced as so:

## Sources

1. Saibian, Sbiis. Hyper-E Numbers