# Names of large numbers

(Redirected from Septillion)

Naming very large numbers is relatively easy. There are two main ways of naming a number: scientific notation and naming by grouping. For example, the number 500,000,000,000,000,000,000 can be called 5 × 1020 in scientific notation since there are 20 zeros behind the 5. If the number is named by grouping, it is five hundred quintillion (American) or 500 trillion (European).

When large numbers have many different decimals in them, such as 642 500 000 000, naming them with scientific notation is about the same, but with one difference. Still counting the number of numbers after the first number (in this case, after the 6 there are 11 numbers) you need to include the ones that are not zero in the formula, but after a decimal point. So 642 500 000 000 will be 6.425 × 1011. When naming by grouping, each group is the name of the group. With the same number, it would be said to be 642 billion, 500 million (US) or 642 milliard, 500 million (Eur).

## Some examples

Number Scientific notation Grouping
6 000 000 000 000 000 6 × 1015 6 quadrillion
765 476 250 000 000 7.6547625 × 1014 765 trillion, 476 billion, 250 million
123 456 789 1.23456789 × 108 123 million, 456 thousand, 789
145 000 1.45 × 105 145 thousand

## Forms of numbering

The American way or "Short form" for naming large numbers is different from the European way or "Long form" of naming large numbers. This is mainly because of American finance. Short form numbering is based on thousands and Long form is based on millions. Because of this, in Short form a billion is one thousand millions (109) while in Long form it is one million millions (1012). The change in the United Kingdom to Short form numbering happened in 1974. Today, Short form is most commonly used in most English speaking countries.

## Names for large numbers

Scientific
notation
American name

(Short Form)

Old European name

(Long Form)

Old-British name SI Symbol Metric prefix
1 One One One
10 Ten Ten Ten da Deca-
100 Hundred Hundred Hundred h Hecto-
1,000 Thousand Thousand Thousand k Kilo-
10,000 Ten thousand Ten thousand Ten thousand
100,000 Hundred thousand Hundred thousand Hundred thousand
106 Million Million Million M Mega-
109 Billion Milliard Thousand million G Giga-
1012 Trillion Billion Billion T Tera-
1015 Quadrillion Billiard Thousand billion P Peta-
1018 Quintillion Trillion Trillion E Exa-
1021 Sextillion Trilliard Thousand trillion Z Zetta-
1030 Nonillion Quintillion Quintillion Q Quetta-
1033 Decillion Quintilliard Thousand quintillion
1036 Undecillion Sextillion Sextillion
1039 Duodecillion Sextilliard Thousand sextillion
1042 Tredecillion Septillion Septillion
1045 Quattuordecillion Septilliard Thousand septillion
1048 Quindecillion Octillion Octillion
1051 Sexdecillion Octilliard Thousand octillion
1054 Septendecillion Nonillion Nonillion
1057 Octodecillion Nonilliard Thousand nonillion
1060 Novemdecillion Decillion Decillion
1063 Vigintillion Decilliard Thousand decillion
1066 Unvigintillion Undecillion Undecillion
1069 Duovigintillion Undecilliard Thousand undecillion
1072 Trevigintillion Duodecillion Duodecillion
1075 Quattuorvigintillion Duodecilliard Thousand duodecillion
1078 Quinvigintillion Tredecillion Tredecillion
1081 Sexvigintillion Tredecilliard Thousand tredecillion
1084 Septenvigintillion Quattuordecillion Quattuordecillion
1087 Octovigintillion Quattuordecilliard Thousand quattuordecillion
1090 Novemvigintillion Quindecillion Quindecillion
1093 Trigintillion Quindecilliard Thousand quindecillion
1096 Untrigintillion Sexdecillion Sexdecilion
1099 Duotrigintillion Sexdecilliard Thousand sexdecillion
10100 Googol Googol Googol
10153 Quinquagintillion Quinvigintilliard
10183 Sexagintillion Trigintilliard
10213 Septuagintillion Quintrigintilliard
10303 Centillion Quinquagintilliard
10603 Ducentillion
103003 Millinillion
1010100 Googolplex
10101034 Skewes' Number
10googolplex Googolplexplex

There is also the number googol, which is a 1 with 100 zeros behind it (10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000), and the number googolplex, which is a 1 with a googol of zeros behind it, (1010,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000) (1010100). The number googolplexplex, is a 1 with a googolplex number of zeros behind it.

The name centillion was devised in the 19th century for the 100th "illion", being 10303 in short form and 10600 in long form, and is much bigger than googol.