| 词条 | 911 (number) |
| 释义 |
| number = 911 | prime = Yes }} 911 (nine hundred [and] eleven) is the integer 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.[1] There are 911 inverse semigroups of order 7 {{OEIS|id=A001428}} 911 is obtained by concatenating its product of digits and sum of digits. As "911" or "9/11", typically pronounced "nine-eleven", it is commonly used to refer the calendar dates November 9 or September 11, depending on which date notation is used. The latter usage most commonly refers to the North American emergency telephone number, see 9-1-1, or the September 11, 2001 attacks in the United States. See also
References1. ^{{Cite OEIS|1=A062786|2=Centered 10-gonal numbers|accessdate=2016-06-02}} {{Integers|9}}{{DEFAULTSORT:911 (Number)}} 1 : Integers |
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