61 (number) Article Index for
61
 

Information About

61 (number)





IN MATHEMATICS

It is the 18th Prime Number . The previous is 59 , with which it comprises a Twin Prime . Sixty-one is a Cuban Prime of the form p = (x^3 - y^3) / (x - y), x = y + 1.

Sixty-one might be the largest prime that divides the product of the next two primes plus 1. If there is a larger such prime, it would have to be greater than 179424673.

Sixty-one is the sum of two squares, 52 + 62, and it is also a Centered Square Number , a Centered Hexagonal Number and a Centered Decagonal Number .

It is also a Keith Number , because it recurs in a Fibonacci-like sequence started from its base 10 digits: 6, 1, 7, 8, 15, 23, 38, 61...


IN SCIENCE


In the Periodic Table

The chemical element with the Atomic Number 61 ( Promethium ), a lanthanide, is the element with the secondary lowest ordinal number, which does not possess any stable isotopes. The promethium preceding element with Atomic Number 60 ( Neodymium ) and the promethium following element 62 ( Samarium ) have all stable isotopes.


In Astronomy


: Messier Object M61 , a Magnitude 10.5 Galaxy in the Constellation Virgo

: The , a double Spiral Galaxy in the constellation Pisces

:The series which began on -973 May 10 and ended on 289 June 5 . The duration of Saros series 61 was 1262.1 years, and it contained 71 solar eclipses.

:The Saros number of the Lunar Eclipse series which began on -870 October 20 and ended on 609 March 26 . The duration of Saros series 61 was 1478.4 years, and it contained 83 lunar eclipses.


IN OTHER FIELDS

Sixty-one is:


REFERENCE


  • R. Crandall and C. Pomerance, Prime Numbers: A Computational Perspective, Springer, NY, 2005, p. 79