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The octocentillion is equal to $$10^{327}$$ in the short scale and $$10^{648}$$ in the long scale.[1]

In the long scale, $$10^{327}$$ is called quattuorquinquagintilliard.

Aarex Tiaokhiao gave the name cennillion, referring to the value of this number.[2]

## Approximations

For short scale:

Notation Lower bound Upper bound
Scientific notation $$1\times10^{327}$$
Arrow notation $$10\uparrow327$$
Steinhaus-Moser Notation 150[3] 151[3]
Copy notation 9[327] 10[164]
Taro's multivariable Ackermann function A(3,1083) A(3,1084)
Pound-Star Notation #*((4375))*11 #*((4376))*11
BEAF {10,327}
Hyper-E notation E327
Bashicu matrix system (0)(0)(0)(0)(0)(0)(0)[358] (0)(0)(0)(0)(0)(0)(0)[359]
Hyperfactorial array notation 178! 179!
Fast-growing hierarchy $$f_2(1076)$$ $$f_2(1077)$$
Hardy hierarchy $$H_{\omega^2}(1076)$$ $$H_{\omega^2}(1077)$$
Slow-growing hierarchy $$g_{\omega^{\omega^23+\omega2+7}}(10)$$

For long scale:

Notation Lower bound Upper bound
Scientific notation $$1\times10^{648}$$
Arrow notation $$10\uparrow648$$
Steinhaus-Moser Notation 267[3] 268[3]
Copy notation 9[648] 1[649]
Taro's multivariable Ackermann function A(3,2149) A(3,2150)
Pound-Star Notation #*((5258))*15 #*((5259))*15
BEAF {10,648}
Hyper-E notation E648
Bashicu matrix system (0)(0)(0)(0)(0)(0)(0)(0)[339] (0)(0)(0)(0)(0)(0)(0)(0)[340]
Hyperfactorial array notation 313! 314!
Fast-growing hierarchy $$f_2(2141)$$ $$f_2(2142)$$
Hardy hierarchy $$H_{\omega^2}(2141)$$ $$H_{\omega^2}(2142)$$
Slow-growing hierarchy $$g_{\omega^{\omega^26+\omega4+8}}(10)$$