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The googoldeciplex (also known as googoldekaplex or googolplexplexplexplexplexplexplexplexplexplex) is equal to E100#11 = EEEEEEEEEEE100 in Hyper-E notation.[1]

It is also equal to 1010101010101010101010100, or a 1 followed by a googolnoniplex (googolplexplexplexplexplexplexplexplexplex) zeroes. It is 10101010101010101010100+1 digits long.

Writing down the full decimal expansion would take 10101010101010101010100-6 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 SI prefix "deci-" and the number "googolplex".

## Approximations in other notations

Notation Approximation
Up-arrow notation $$57 \uparrow \uparrow 12$$
Chained arrow notation $$57 \rightarrow 12 \rightarrow 2$$
Hyper-E notation $$\textrm{E}100\#11$$ (exact)
Hyperfactorial array notation $$15!1$$
BEAF $$\{57,12,2\}$$
Fast-growing hierarchy $$f^{11}_2(326)$$ ~ $$f_3(11)$$
Hardy hierarchy $$H_{\omega^2{11}}(324)$$
Slow-growing hierarchy $$g_{\varepsilon_0}(12)$$