911 (nine hundred eleven) is the number following 910 and preceding 912.

It is a prime number, a Sophie Germain prime and the sum of three consecutive primes (293 + 307 + 311). It is an Eisenstein prime with no imaginary part and real part of the form 3n − 1. Since 913 is a semiprime, 911 is a Chen prime. It is also a centered decagonal number. In linguistics, cardinal numbers is the name given to number words that are used for quantity (one, two, three), as opposed to ordinal numbers, words that are used for order (first, second, third). ... Commonly, ordinal numbers, or ordinals for short, are numbers used to denote the position in an ordered sequence: first, second, third, fourth, etc. ... In mathematics, factorization or factoring is the decomposition of an object (for example, a number, a polynomial, or a matrix) into a product of other objects, or factors, which when multiplied together give the original. ... The system of Roman numerals is a numeral system originating in ancient Rome, and was adapted from Etruscan numerals. ... The binary numeral system (base 2 numerals) represents numeric values using two symbols, typically 0 and 1. ... james In mathematics and computer science, base-16, hexadecimal, or simply hex, is a numeral system with a radix or base of 16 usually written using the symbols 0–9 and A–F or a–f. ... In mathematics, a prime number (or a prime) is a natural number that has exactly two (distinct) natural number divisors, which are 1 and the prime number itself. ... A prime number p is called a Sophie Germain prime if 2p + 1 is also prime. ... An Eisenstein prime is an Eisenstein integer aω + b that has only two Eisenstein divisors, the complex cube root of unity and aω + b itself. ... In mathematics, a semiprime (also called biprime or 2-almost prime) is a natural number that is the product of two (not necessarily distinct) prime numbers. ... A prime number p is called a Chen prime if p + 2 is either a prime or a semiprime. ... A centered decagonal number is a centered figurate number that represents a decagon with a dot in the center and all other dots surrounding the center dot in successive decagonal layers. ...

911 (nine-one-one) is the telephone number of most local emergency agencies (such as the police or the fire department) in the United States and Canada. A telephone number is a string of decimal digits that uniquely indicates the network termination point. ... Firefighter with an axe A firefighter, sometimes still called a fireman though women have increasingly joined firefighting units, is a person who is trained and equipped to put out fires, rescue people and in some areas provide emergency medical services. ...

As "911" or "9/11", typically pronounced "nine-eleven", it is commonly used to refer the calendar date 9 November, or September 11 where middle endian date notations are used. The latter usage most commonly refers to the September 11, 2001 attacks in the United States that sparked the War on Terrorism. There were exactly 911 days between the 11 September 2001 attack and the March 11 2004 Madrid train bombings. November 9 is the 313th day of the year (314th in leap years) in the Gregorian Calendar, with 52 days remaining. ... September 11 is the 254th day of the year in the Gregorian calendar (255th in leap years). ... Endianness generally refers to sequencing methods used in a one-dimensional system (such as writing or computer memory). ... The explosion resulting from the crashing of United Airlines Flight 175 into the South Tower. ... The War on Terrorism or War on Terror (officially the Global War on Terrorism or GWOT[1]) is a campaign by the NATO governments and their allies governments with the stated goal of ending international terrorism by stopping those groups identified by the U.S. as terrorist groups and ending... September 11 is the 254th day of the year in the Gregorian calendar (255th in leap years). ... The scene of one of the Madrid bombings. ...

9/11 = 0.818181818
9+11 = 20
9-11 = -2
9*11 = 99
9^11 = 31.381.059.609