View source for 101 (number)

{{Use dmy dates|date=January 2023}} 
{{Infobox number  
| number = 101
| cardinal = one hundred [and] one
| ordinal text = one hundred [and] first

| factorization = [[prime number|prime]]
| prime = 26th
| divisor = 1, 101
}}
'''101''' ('''one hundred [and] one''') is the [[natural number]] following [[100 (number)|100]] and preceding [[102 (number)|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 (linguistics)|ordinal number]], 101st (one hundred [and] first), rather than 101th, is the correct form.

101 is a [[prime number]] and the smallest [[integer]] above 100. It is also a [[palindromic number]], and hence, a [[palindromic prime]].

{{Wiktionary|one hundred and one|one hundred one}}

== In mathematics ==
[[File:square-sum-101.png|thumb|101 as the sum of three distinct nonzero squares]]
101 is an [[alternating factorial]], [[sexy prime]] and 101 is also the smallest number that can be expressed as the sum of three distinct nonzero [[square number|squares]] in more than two ways: <math>9^2+4^2+2^2</math>, <math>8^2+6^2+1^2</math> or <math>7^2+6^2+4^2</math> (see image).<ref>{{cite OEIS|A025349|Numbers that are the sum of 3 distinct nonzero squares in 3 or more ways.}}</ref><ref>{{cite OEIS|A025341|Numbers that are the sum of 3 distinct nonzero squares in exactly 3 ways.}}</ref>

For a 3-digit number in decimal, this number has a relatively simple [[divisibility rule|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 <math>1000a+100b+10a+b</math> (where {{mvar|a}} and {{mvar|b}} are integers from 0 to 9), such as 3232 or 9797, or of the form <math>100b+b</math>, such as 707 and 808, then the number is divisible by 101.<ref>{{citation|title=Stupid Divisibility Tricks 101 Ways to Stupefy Your Friends|first=Marc|last=Renault|journal=Math Horizons|volume=14|issue=2|date=November 2006|pages=18–21, 42|doi=10.1080/10724117.2006.11974676|jstor=25678653|s2cid=125269086}}</ref>

==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.

In the book ''[[Nineteen Eighty-Four|1984]]'', written by [[George Orwell]], [[Ministries in Nineteen Eighty-Four|Room 101]] is a designated room used for torture by the [[Thought Police]] of Oceania, where the greatest fear known to the Thought Police is unleashed upon the victim.

==In education==
In [[course (education)#US course numbering system|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.<ref name="mentalfloss">{{cite web |url= http://mentalfloss.com/article/53734/why-are-introductory-classes-called-101 |title= Why Are Introductory Classes Called '101'? |language=en |last= Kovalchik  |first= Kara |date=2013-11-20 |website=mentalfloss.com |access-date=2023-09-30}}</ref><ref name=Forest>Forest, J.J.F. (2002) ''Higher education in the United States: an encyclopedia'' [https://books.google.com/books?id=sFFX9OIkF2IC&dq=course%20numbering%20systems&pg=PA73 p.73.] ABC-CLIO. {{ISBN|1-57607-248-7}}. Retrieved October 2011</ref><ref name="Slate">{{cite web|last=Engber|first=Daniel|title=101 101|url=http://www.slate.com/articles/news_and_politics/explainer/2006/09/101_101.html|website=Slate Magazine|access-date=9 May 2017|date=6 September 2006}}</ref> This common numbering system was designed to make [[articulation (education)|transfer between colleges]] easier. It can also indicate a course for students not intending to major in the subject; e.g. a student intending to major in English would take ''English 111'' not ''English 101''. 

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.<ref name=Forest/> One of earliest such usages, perhaps the first, was by the [[University of Buffalo]] in 1929.<ref name=Forest/><ref name=Slate/>  However, this convention is not universally prevalent.  For example, at the various University of California campuses, all three-digit numbers including 101 denote upper division courses that typically have prior coursework in the subject as prerequisites.<ref>https://registrar.ucla.edu/academics/course-descriptions/course-numbering-and-description-guide</ref>

Based on this usage, the term "[[wikt:101|101]]" (pronounced {{IPAc-en|ˌ|w|ʌ|n|oʊ|ˈ|w|ʌ|n}} {{Respell|WUN|oh|WUN}}) has gained a slang sense referring to basic knowledge of a topic or a collection of introductory materials to a topic, as in the sentence, "Boiling potatoes is Cooking 101".<ref name=Slate/> The ''[[Oxford English Dictionary]]'' records the usage of "101" in this slang sense from 1986.<ref name=Slate/>

==In other fields==
{{Main|101 (disambiguation){{!}}101}}

In public life:

* In [[Hinduism]], 101 is a lucky number.
* [[101st kilometre]], a condition of release from the [[Gulag]] in the Soviet Union.
* 101 is the main Police Emergency Number in [[Belgium]].
* [[101 Non-Emergency Number|101]] is the [[SNEN|Single Non-Emergency Number (SNEN)]] in some parts of the UK, a telephone number used to call emergency services that are urgent but not emergencies. 101 is now available across all areas of England and Wales.<ref>{{cite web|url=http://www.direct.gov.uk/en/CrimeJusticeAndTheLaw/Reportingcrimeandantisocialbehaviour/DG_185338|title=Report a crime or antisocial behaviour – GOV.UK|website=direct.gov.uk|access-date=4 April 2018}}</ref><ref>{{citation
|url=http://www.101.gov.uk
|title=Welcome to 101
|access-date=5 April 2009
|publisher=[[Home Office]]
}}</ref>

In technology:
* An [[HTTP status code]] indicating that the server is switching protocols as requested by the client to do so.

==References==
{{Commons category}}
* Wells, D. ''[[The Penguin Dictionary of Curious and Interesting Numbers]]'' London: Penguin Group. (1987): page 133. {{ISBN|978-0-14-008029-2}}
{{Reflist}}
{{Integers|1}}

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[[Category:Integers]]
[[Category:Academic slang]]