| 91 (number) |
Article Index for 91 |
Information About91 (number) |
IN MATHEMATICS Ninety-one is a Triangular Number and a Hexagonal Number , one of the few such numbers to also be a Centered Hexagonal Number , and it is also a Centered Nonagonal Number and a Centered Cube Number . It is the sum of the squares of the first six Integer s. It is also the lowest natural number which looks prime but isn't, because neither of its factors 7 and 13 have simple Divisibility tests. It is the smallest positive integer expressible as a sum of two cubes in two different ways if negative roots are allowed: 91 = 63+(-5)3 = 43+33. (See 1729 for more details). It is also the smallest Pseudoprime satisfying the congruence 3''n'' = 3 mod ''n''. IN SCIENCE
In Astronomy , : Messier Object M91 , a Magnitude 11.5 Spiral Galaxy in the Constellation Coma Berenices : The , a single Star in the constellation Andromeda :The series which began on August 6 159 BC and ended on 1175 October 16 . The duration of Saros series 91 was 1334.2 years, and it contained 75 solar eclipses. :The Saros number of the Lunar Eclipse series which began on 161 May 26 and ended on 1459 July 15 . The duration of Saros series 91 was 1298.1 years, and it contained 73 lunar eclipses. IN OTHER FIELDS Ninety-one is also:
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