## FANDOM

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This page is about Bowers's definition. For the alternative definition, see novemdecillion.

The icosillion (alternately icocillion or ducontillion[1]) is equal to $$10^{3\left(10^{60}\right)+3}$$ or $$10^{3\text{ novemdecillion }3}$$.[2] The term was coined by Jonathan Bowers.

## Etymology

The name of this number is based on the suffix "-illion" and the prefix "icosa-" (from Greek 20).

## Approximations in other notations

Notation Lower bound Upper bound
Arrow notation $$1000\uparrow(1+10\uparrow60)$$
Down-arrow notation $$1000\downarrow\downarrow21$$ $$536\downarrow\downarrow23$$
Steinhaus-Moser Notation 37[3][3] 38[3][3]
Copy notation 2[2[61]] 3[3[61]]
H* function H(H(19))
Taro's multivariable Ackermann function A(3,A(3,199)) A(3,A(3,200))
Pound-Star Notation #*((1))*(2)*91 #*((1))*(7,3,1,4)*6
BEAF {1000,1+{10,60}}
Hyper-E notation E(3+3E60)
Bashicu matrix system (0)(1)[198] (0)(1)[199]
Hyperfactorial array notation (46!)! (47!)!
Fast-growing hierarchy $$f_2(f_2(195))$$ $$f_2(f_2(196))$$
Hardy hierarchy $$H_{\omega^22}(195)$$ $$H_{\omega^22}(196)$$
Slow-growing hierarchy $$g_{\omega^{\omega^{\omega6}3+3}}(10)$$