Names of Large and Small Numbers

It's often easier to express very large numbers using exponents, however names are available if that's what you need.

The first few names are familiar: ten, hundred, thousand and million. After that, a name is assigned to each number that is a thousand times greater, as follows:

Name	Number
ten	10
hundred	100
thousand	1000
million	106
billion	109
trillion	1012
quadrillion	1015
quintillion	1018
sextillion	1021
septillion	1024
octillion	1027
nonillion	1030
decillion	1033
undecillion	1036
dodecillion	1039
tredecillion	1042
quattuordecillion	1045
quindecillion	1048
sexdecillion	1051
septdecillion	1054
octodecillion	1057
novemdecillion	1060
vigintillion	1063
unvigintillion	1066
duovigintillion	1069
trevigintillion	1072
quattuorvigintillion	1075
quinvigintillion	1078
sexvigintillion	1081
septvigintillion	1084
octovigintillion	1087
novemvigintillion	1090
trigintillion	1093
untrigintillion	1096
duotrigintillion	1099

Larger numbers

There's not a lot of point going further, as 10⁹⁹ is greater than the number of particles in the universe, but that hasn't stopped people from coining names for larger numbers. One googol is 10¹⁰⁰, and one googolplex is 10^{1 googol}.

One centillion is 10³⁰³, a ducentillion is 10⁶⁰³ and a trecentillion is 10⁹⁰³, and there are also names for all the powers of a thousand in between those.

Variations

The names of large numbers are not officially standardised, and variations are found. For example, the dodecillion is sometimes the duodecillion, and the septdecillion can be the septendecillion.

Milliards and the "British large numbers"

It's frequently claimed that British usage differs; that it includes milliard between million and billion, billiard between billion and trillion, etc. As a consequence, a British billion would be 10¹² and a British trillion would be 10¹⁸.

This system echoes the French (milliard) and German (Milliarde), and had substantial historic usage in Britain. However, it's not in use in any practical way in the United Kingdom today, other than as a topic of conversation for pedants. In newspapers and on television, billion always means 10⁹ and trillion always means 10¹². In government statistics 10⁹ has been a billion since 1974[1].

So forget about all those dusty old tables of large numbers that still show 10³³ as a quintilliard rather than as a decillion.

Names of small numbers

For the most part, the names of small numbers match the names of the large numbers with the suffix "-th" added:

Name	Number
tenth	1/10
hundredth	1/100
thousandt	1/1000
millionth	10-6
billionth	10-9
trillionth	10-12
quadrillionth	10-15
quintillionth	10-18
sextillionth	10-21
septillionth	10-24
octillionth	10-27
nonillionth	10-30
decillionth	10-33

One part in a googolplex, however, breaks the pattern and is called a googolminex[2].

Additional information

Landon Noll has a very comprehensive page on this subject, ending with a poignant anecdote telling how miffed he was when the teacher wrote "over 100" when, in response to the challenge "how high can you count" he got to 21603 and was still going when the teacher stopped him. And no, his name is not Landon Knol.