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An unvigintillion is equal to 1066 in short scale, or 10126 in long scale by Conway and Guy's naming system[1][2][3] or by Rowlett's naming system.[4]

In the long scale, 1066 is called undecillion, which is commonly used in France and Germany.

Sbiis Saibian uses the term viginti-untillion for this number, since the order of terms should reverse after the 20th -illion, because on thirteen ~ nineteen the one's digit comes first, while on twenty-one and onwards the ten's digit comes first.[5]

## Examples

• The number of arrangements possible on a deck of cards is equal to 52!, which is approximately 80 unvigintillion.

## Approximations

For short scale:

Notation Lower bound Upper bound
Scientific notation $$1\times10^{66}$$
Arrow notation $$10\uparrow66$$
Steinhaus-Moser Notation 40[3] 41[3]
Copy notation 9[66] 1[67]
Taro's multivariable Ackermann function A(3,216) A(3,217)
Pound-Star Notation #*(10,4,2,2,0,1)*8 #*(10,0,6,3,4,4)*7
BEAF {10,66}
Hyper-E notation E66
Bashicu matrix system (0)(0)(0)(0)[13335] (0)(0)(0)(0)[13336]
Hyperfactorial array notation 50! 51!
Fast-growing hierarchy $$f_2(211)$$ $$f_2(212)$$
Hardy hierarchy $$H_{\omega^2}(211)$$ $$H_{\omega^2}(212)$$
Slow-growing hierarchy $$g_{\omega^{\omega6+6}}(10)$$

For long scale:

Notation Lower bound Upper bound
Scientific notation $$1\times10^{126}$$
Arrow notation $$10\uparrow126$$
Steinhaus-Moser Notation 68[3] 69[3]
Copy notation 9[126] 1[127]
Taro's multivariable Ackermann function A(3,415) A(3,416)
Pound-Star Notation #*(0,11,3,10,10,4,8,1)*9 #*(1,11,3,10,10,4,8,1)*9
BEAF {10,126}
Hyper-E notation E126
Bashicu matrix system (0)(0)(0)(0)(0)[8659] (0)(0)(0)(0)(0)[8660]
Hyperfactorial array notation 83! 84!
Fast-growing hierarchy $$f_2(409)$$ $$f_2(410)$$
Hardy hierarchy $$H_{\omega^2}(409)$$ $$H_{\omega^2}(410)$$
Slow-growing hierarchy $$g_{\omega^{\omega^2+\omega2+6}}(10)$$

## List of prefixed numbers derived from vigintillion

Name Short scale Long scale
unvigintillion 1066 10126
duovigintillion 1069 10132
trevigintillion 1072 10138
quattuorvigintillion 1075 10144
quinvigintillion 1078 10150
sexvigintillion 1081 10156
septenvigintillion 1084 10162
octovigintillion 1087 10168
novemvigintillion 1090 10174