-yllion

-yllion is a proposal from Donald Knuth for the terminology and symbols of an alternate decimal superbase system. In it, he adapts the familiar English terms for large numbers to provide a systematic set of names for much larger numbers. In addition to providing an extended range, "-yllion" also dodges the long and short scale ambiguity of -illion.

Knuth's digit grouping is exponential instead of linear; each division doubles the number of digits handled, whereas the familiar system only adds three or six more. His system is basically the same as one of the ancient and now-unused Chinese numeral systems, in which units stand for 10⁴, 10⁸, 10¹⁶, 10³², and so on.

Details and examples

In Knuth's "-yllion" proposal:
*1 to 99 have their usual names.
*100 to 9999 are divided before the 2nd-last digit and named "blah" hundred "blah". (e.g. 1234 is "twelve hundred thirty-four"; 7623 is "seventy-six hundred twenty-three")
*10⁴ to 10⁸-1 are divided before the 4th-last digit and named "blah" myriad "blah". Knuth also introduces at this level a grouping symbol (comma) for the numeral. So, 382,1902 is "3 hundred 82 myriad 19 hundred 2".
*10⁸ to 10¹⁶-1 are divided before the 8th-last digit and named "blah" myllion "blah", and a semicolon separates the digits. So 1,0002;0003,0004 is "1 myriad 2 myllion 3 myriad 4"
*10¹⁶ to 10³²-1 are divided before the 16th-last digit and named "blah" byllion "blah", and a colon separates the digits. So 12:0003,0004;0506,7089 is "12 byllion 3 myriad 4 myllion 5 hundred 06 myriad 70 hundred 89"
*etc.Each new number name is the square of the previous one — therefore, each new name covers twice as many digits. Knuth continues borrowing the traditional names changing "illion" to "yllion" on each one. Abstractly, then, "one n-yllion" is $10^\{2^\{n+2$. "One trigintyllion" would have nearly forty-three myllion digits.

ee also

*Alternatives to Knuth's proposal that date back to the French Renaissance came from Nicolas Chuquet and Jacques Peletier du Mans.
*A related proposal by Knuth is his up-arrow notation.

References

* Donald E. Knuth. "Supernatural Numbers" in The Mathematical Gardener (edited by D. A. Klarner). Wadsworth, Belmont, CA, 1981. 310—325.
* Robert P. Munafo. " [http://home.earthlink.net/~mrob/pub/math/largenum.html Large Numbers] ", 1996-2008.