Icosehectillion is equal to \(10^{3\cdot10^{360} + 3}\).[1][2] It is defined using Sbiis Saibian's generalization of Jonathan Bowers' -illion system.
Approximations[]
| Notation | Lower bound | Upper bound |
|---|---|---|
| Arrow notation | \(1000\uparrow(1+10\uparrow360)\) | |
| Down-arrow notation | \(1000\downarrow\downarrow121\) | \(12\downarrow\downarrow335\) |
| Steinhaus-Moser Notation | 161[3][3] | 162[3][3] |
| Copy notation | 2[2[361]] | 3[3[361]] |
| H* function | H(H(119)) | |
| Taro's multivariable Ackermann function | A(3,A(3,1196)) | A(3,A(3,1197)) |
| Pound-Star Notation | #*((1))*((48))*9 | #*((1))*((49))*9 |
| BEAF | {1000,1+{10,360}} | |
| Hyper-E notation | E(3+3E360) | |
| Bashicu matrix system | (0)(1)[34] | (0)(1)[35] |
| Hyperfactorial array notation | (192!)! | (193!)! |
| Fast-growing hierarchy | \(f_2(f_2(1188))\) | \(f_2(f_2(1189))\) |
| Hardy hierarchy | \(H_{\omega^22}(1188)\) | \(H_{\omega^22}(1189)\) |
| Slow-growing hierarchy | \(g_{\omega^{\omega^{\omega^23+\omega6}3+3}}(10)\) | |