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# 105 (number)

105 (one hundred [and] five) is the natural number following 104 and preceding 106. It is the double factorial of 7.

 Cardinal one hundred [and] five Ordinal 105th Factorization $3 \cdot 5 \cdot 7$ Divisors 3, 5, 7, 15, 21, 35 Roman numeral CV Binary 1101001 Hexadecimal 69

## In mathematics

105 is a triangular number and a 12-gonal number as well as a sphenic number and a Zeisel number. It comes in the middle of the prime quadruplet (101, 103, 107, 109). The only other such odd numbers less than a thousand are 15, 195 and 825. 105 is also a pseudoprime to the prime bases: 13, 29, 41, 43, 71, 83 and 97.

One hundred five is also a number n for which n - 2k is prime, for k < log2(n). (This even works up to k = 8, ignoring the negative sign.)

## In science

In astronomy,

Messier object M105, a magnitude 11.0 elliptical galaxy in the constellation Leo
The New General Catalogue object NGC105 , a magnitude 13.2 spiral galaxy in the constellation Pisces
Asteroid 105 Artemis
The Saros number of the solar eclipse series which began on 499 March 27 and ended on 1779 May 16. The duration of Saros series 105 was 1280.1 years, and it contained 72 solar eclipses.
The Saros number of the lunar eclipse series which began on 566 August 16 and ended on 1882 October 26. The duration of Saros series 105 was 1316.2 years, and it contained 74 lunar eclipses.

## In other fields

105 is also:

Last updated: 05-24-2005 19:08:46