121 (number)
Encyclopedia
121 is the natural number
following 120
and preceding 122
.
s (37 + 41 + 43). There are no squares besides 121 known to be of the form
, where p is prime (3, in this case). Other such squares must have at least 35 digits.
There are only two other squares known to be of the form n! + 1, supporting Brocard's conjecture. Another example of 121 being of the few examples supporting a conjecture is that Fermat conjectured that 4 and 121 are the only perfect squares of the form x3 - 4 (with x being 2 and 5, respectively).
It is also a star number
and a centered octagonal number
.
In base 10, it is a Smith number
since its digits add up to the same value as its factorization (which uses the same digits) and as a consequence of that it is a Friedman number
(11^2). But it can not be expressed as the sum of any other number plus that number's digits, making 121 a self number
.
Natural number
In mathematics, the natural numbers are the ordinary whole numbers used for counting and ordering . These purposes are related to the linguistic notions of cardinal and ordinal numbers, respectively...
following 120
120 (number)
120 is the natural number following 119 and preceding 121. 120 was known as "the great hundred", especially prior to the year 1700, from the Teutonic Hundert which equalled 120. The number 100, now known commonly as "one hundred" was then known as "the small hundred". It is also known as...
and preceding 122
122 (number)
122 is the natural number following 121 and preceding 123.-In mathematics:It is a nontotient since there is no integer with exactly 122 coprimes below it...
.
In mathematics
One hundred [and] twenty-one is a square and is the sum of three consecutive primePrime number
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number. For example 5 is prime, as only 1 and 5 divide it, whereas 6 is composite, since it has the divisors 2...
s (37 + 41 + 43). There are no squares besides 121 known to be of the form
, where p is prime (3, in this case). Other such squares must have at least 35 digits.There are only two other squares known to be of the form n! + 1, supporting Brocard's conjecture. Another example of 121 being of the few examples supporting a conjecture is that Fermat conjectured that 4 and 121 are the only perfect squares of the form x3 - 4 (with x being 2 and 5, respectively).
It is also a star number
Star number
A star number is a centered figurate number that represents a centered hexagram, such as the one that Chinese checkers is played on.The nth star number is given by the formula 6n + 1...
and a centered octagonal number
Centered octagonal number
A centered octagonal number is a centered figurate number that represents an octagon with a dot in the center and all other dots surrounding the center dot in successive octagonal layers...
.
In base 10, it is a Smith number
Smith number
A Smith number is a composite number for which, in a given base , the sum of its digits is equal to the sum of the digits in its prime factorization. For example, 378 = 2 × 3 × 3 × 3 × 7 is a Smith number since 3 + 7 + 8 =...
since its digits add up to the same value as its factorization (which uses the same digits) and as a consequence of that it is a Friedman number
Friedman number
A Friedman number is an integer which, in a given base, is the result of an expression using all its own digits in combination with any of the four basic arithmetic operators and sometimes exponentiation. For example, 347 is a Friedman number since 347 = 73 + 4...
(11^2). But it can not be expressed as the sum of any other number plus that number's digits, making 121 a self number
Self number
A self number, Colombian number or Devlali number is an integer which, in a given base, cannot be generated by any other integer added to the sum of that other integer's digits. For example, 21 is not a self number, since it can be generated by the sum of 15 and the digits comprising 15, that is,...
.
In other fields
121 is also:- The electricityElectricityElectricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
emergency telephone numberEmergency telephone numberMany countries' public telephone networks have a single emergency telephone number, sometimes known as the universal emergency telephone number or occasionally the emergency services number, that allows a caller to contact local emergency services for assistance. The emergency telephone number may...
in EgyptEgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world... - The number for voicemailVoicemailVoicemail is a computer based system that allows users and subscribers to exchange personal voice messages; to select and deliver voice information; and to process transactions relating to individuals, organizations, products and services, using an ordinary telephone...
for mobile phoneMobile phoneA mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s on the VodafoneVodafoneVodafone Group Plc is a global telecommunications company headquartered in London, United Kingdom. It is the world's largest mobile telecommunications company measured by revenues and the world's second-largest measured by subscribers , with around 341 million proportionate subscribers as of...
network - The undiscovered chemical elementChemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
UnbiuniumUnbiuniumUnbiunium , also known as eka-actinium or element 121, is the temporary name of a hypothetical chemical element in the periodic table that has the temporary symbol Ubu and has the atomic number 121. It would be the first element in the g-block of the periodic table...
has the atomic number 121 - The official end score for CribbageCribbageCribbage, or crib, is a card game traditionally for two players, but commonly played with three, four or more, that involves playing and grouping cards in combinations which gain points...
See also
- List of highways numbered 121
- United States House of Representatives House Resolution 121United States House of Representatives House Resolution 121United States House of Representatives House Resolution 121 is a resolution about comfort women which Japanese-American Congressman Mike Honda of California's 15th congressional district introduced to the American House of Representatives in 2007...
- United Nations Security Council Resolution 121United Nations Security Council Resolution 121United Nations Security Council Resolution 121, adopted unanimously on December 12, 1956, after examining the application of the Empire of Japan for membership in the United Nations, the Council recommended to the General Assembly that Japan be admitted....