|Cardinal||one hundred [and] one|
(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.
Given 101, the Mertens function returns 0. It is the second prime to have this property.
For a 3-digit number in decimal, 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 (where a and b are integers from 0 to 9), such as 3232 or 9797, or of the form , 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.
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.
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. One of earliest such usages, perhaps the first, was by the University of Buffalo in 1929.
Based on this usage, the term "101" (pronounced ONE-oh-ONE) 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". The Oxford English Dictionary records the usage of "101" in this slang sense from 1986.
Main article: 101