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Fugafour is equal to 443 = 464 = 2128 = 227, or $$4 \downarrow \downarrow 4$$ using down-arrow notation. The name is formed by applying the fuga- prefix to 4.[1][2][3] It is approximately 3.4028*1038 using scientific notation, and it is about 340 undecillion in the short scale or 340 sextillion in the long scale.

It is also the number of possible IPv6 addresses.

## Decimal expansion

340,282,366,920,938,463,463,374,607,431,768,211,456

## Approximations

Notation Lower bound Upper bound
Scientific notation $$3.402\times10^{38}$$ $$3.403\times10^{38}$$
Arrow notation $$4\uparrow4\uparrow3$$
Steinhaus-Moser Notation 26[3] 27[3]
Copy notation 3[39] 4[39]
Taro's multivariable Ackermann function A(3,125) A(3,126)
Pound-Star Notation #*(4,2,3,4,8)*5 #*(4,5,1,5,1)*6
BEAF {4,{4,3}}
Hyper-E notation E[4]3#2
Bashicu matrix system (0)(0)(0)[65536]
Hyperfactorial array notation 34! 35!
Strong array notation s(4,(4,3))
Fast-growing hierarchy $$f_2(121)$$ $$f_2(122)$$
Hardy hierarchy $$H_{\omega^2}(121)$$ $$H_{\omega^2}(122)$$
Slow-growing hierarchy $$g_{\omega^{\omega^3}}(4)$$