101 102 → Factorization prime Divisors 1, 101 | Cardinal one hundred [and] one Prime 26th | |

Ordinal 101st
(one hundred [and] first) |

**101** (**one hundred [and] one**) is the natural number following 100 and preceding 102.

It is variously pronounced "one hundred and one" / "a hundred and one", "one hundred one" / "a hundred one", and "one oh one". As an ordinal number, 101st (one hundred [and] first), rather than 101th, is the correct form.

## Contents

## In mathematics

**101** is:

^{n}+ 1.

Given 101, the Mertens function returns 0. It is the second prime having this property.

The decimal representation of 2^{101} − 1 is 2 535301 200456 458802 993406 410751. The prime decomposition of that is 7 432339 208719 x 341117 531003 194129

For a 3-digit number in base 10, this number has a relatively simple divisibility test. The candidate number is split into groups of four, starting with the rightmost four, and added up to produce a 4-digit number. If this 4-digit number is of the form 1000*a* + 100*b* + 10*a* + *b* (where *a* and *b* are integers from 0 to 9), such as 3232 or 9797, or of the form 100*b* + *b*, such as 707 and 808, then the number is divisible by 101.

On the seven-segment display of a calculator, 101 is both a strobogrammatic prime and a dihedral prime.

## In science

## In books

According to Books in Print, more books are now published with a title that begins with '101' than '100'. They usually describe or discuss a list of items, such as *101 Ways to...* or *101 Questions and Answers About...* . This marketing tool is used to imply that the customer is given a little extra information beyond books that include only 100 items. Some books have taken this marketing scheme even further with titles that begin with '102', '103', or '1001'. The number is used in this context as a slang term when referring to "a 101 document" what is usually referred to as a statistical survey or overview of some topic.

Room 101 is a torture chamber in the novel *Nineteen Eighty-Four* by George Orwell.

Creative Writing 101 by Raymond Carver, "A writer's values and craft. This was what the man (John Gardner) taught and what he stood for, and this is what I've kept by me in the years since that brief but all important time."

## In education

In American university course numbering systems, the number 101 is often used for an introductory course at a beginner's level in a department's subject area. This common numbering system was designed to make transfer between colleges easier. In theory, any numbered course in one academic institution should bring a student to the same standard as a similarly numbered course at other institutions.

Based on this usage, the term "101" has been extended to mean an introductory level of learning or a collection of introductory materials to a topic.

## In other fields

*Topic*101" is used generally to indicate the basics of any subject. Used this way, it is always pronounced "one-oh-one".

*101 Dalmatians*

*The Wonderful 101*