duocentillion

From duo- (“two”) +‎ centillion. Compare Latin ducentī (“two hundred”). Coined by Alfred Holbrook, a principal of South-Western Normal School in Lebanon, Ohio, in 1859 (see the quotation).

duocentillion (plural duocentillions)

1. (rare, short scale) 10³⁰⁹.
   • [1859, Alfred Holbrook, “Theoretical Arithmetic”, in The Normal: or, Methods of Teaching the Common Branches, […], New York, N.Y.: […] A[lfred] S[mith] Barnes & Burr, […], →OCLC, page 306:

     Names of the Periods.—1st, Units. 2d, Thousands. 3d, Millions. 4th, Billions. 5th, Trillions. 6th, Quadrillions. 7th, Quintillions. 8th, Sextillions. 9th, Septillions. 10th. Octillions. 11th, Nonillions. 12th, Decillions. 13th, Undecillions. 14th, Duodecillions. 15th, Tridecillions. 16th, Quadrodecillions. 17th, Quindecillions. 18th, Sexdecillions. 19th, Septodecillions. 20th, Octodecillions. 21st, Nonodecillions. 22d. Vingintillions.^[sic] 23d, Unvingintillions. 24th, Duo-vingintillions, etc. 32d, Trigintillions. 42d, Quadrogintillions, 52d, Quingintillions. 62d, Sexagintillions. 72d, Septuagintillions. 82d, Octogintillions. 92d, Ninogintillions. 102d, Centillions. 103d, Uncentillions. 104th, Duocentillions, etc. 202d, Duocentillions,^{[sic – meaning Ducentillions]} etc. 1002d, Millillions, etc.]

   • 2004, Brian Campbell, “Conte”, in Lenore Langs, Laurie Smith, editors, Continuum: Time, the Fourth Dimension, Windsor, Ont.: Cranberry Tree Press, →ISBN; republished as Brian Campbell, “Conte”, in Sky of Ink‎^[1], 4 December 2004, archived from the original on 5 November 2016:

     "Upon." This upon. Upon a time. How upon? A time, especially a time? How can anyone be upon a time? Why not within? Without? Inside? Out? Under, over, in front of, back of, beside, above, beyond? "Twice beneath a time." "Thrice beyond a time." "One hundred thousand three hundred and forty-six nonagintillion duocentillion sextendecillion times without…" …a time? Why not space? Space-time time-space space-time times time-space?

   • 2014 March 1, Patrick LeMieux, “Histories of the Future”, in Electronic Book Review‎^[2], →ISSN, →OCLC, archived from the original on 11 September 2025:

     Despite the fact that 2¹⁰²⁴ is a discrete number, that each of its 309 digits are known quantities, and that mathematical operations may be carried out both with and within it, enumeration of such a figure not only outpaces human consciousness but time and space. We cannot count to a duocentillion.

   • 2022 [2003], László Krasznahorkai, translated by Ottilie Mulzet, chapter XXXVIII, in A Mountain to the North, a Lake to the South, Paths to the West, a River to the East, New York, N.Y.: New Directions Publishing, →ISBN:

     [T]here followed one undecicentillion duocentillion, and from there, toward the end of the book there ensued the following shocking number, which, even if he did not denote it with letters but only with numbers of course, as he had done up till now, namely, there then came the number of nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine-undecicentillion, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine-duocentillion, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine-nonaginta-tredecillion, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine-nonaginta-nonillion, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine-nonaginta-septillion, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine-nonaginta-quintillion, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine nonaginta-trillion, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine nonaginta-million, nine-hundred-ninety-nine-thousand-nine-hundred-ninety-nine nonagintillion, so that here, with the usual ellipses, he indicated that he was going to jump forward a bit, namely he jumped forward by immeasurable quantities, then suddenly he informed his readers that from this point onward he would make use of exponential notation, […]

   • 2025, Andreas Klappenecker, Hyunyoung Lee, “Pigeonhole Principle”, in Discrete Structures (Undergraduate Texts in Mathematics), Cham: Springer, →ISBN, →ISSN, part III (Combinatorics), chapter 11 (Counting), page 297:

     Ernie enthusiastically attempts to write down all possible sequences of 100 die rolls. Bert is flabbergasted and interrupts him. Bert points out that there are 6⁴ = 1296 different combinations of face values of four dice, and Ernie cannot possibly write down all sequences of 100 rolls, as 1296¹⁰⁰ is more than 100 duocentillion.