# 105 (number)

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

 List of numbers — Integers << 100 101 102 103 104 105 106 107 108 109 >>
Cardinal one hundred [and]
five
Ordinal105th
Factorization[itex]3 \cdot 5 \cdot 7[itex]
Divisors 3, 5, 7, 15, 21, 35
Roman numeralCV
Binary1101001

## 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 [itex]n - 2^k[itex] is prime, for [itex]k < log_2(n)[itex]. (This even works up to [itex]k = 8[itex], 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 (http://www.ngcic.org/) NGC105, a magnitude 13.2 spiral galaxy in the constellation Pisces
Asteroid 105 Artemis
The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros1-175.html) 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 (http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1-175.html) 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:

• Art and Cultures
• Musical Instruments (http://academickids.com/encyclopedia/index.php/List_of_musical_instruments)
• Countries of the World (http://www.academickids.com/encyclopedia/index.php/Countries)
• Ancient Civilizations (http://www.academickids.com/encyclopedia/index.php/Ancient_Civilizations)
• Industrial Revolution (http://www.academickids.com/encyclopedia/index.php/Industrial_Revolution)
• Middle Ages (http://www.academickids.com/encyclopedia/index.php/Middle_Ages)
• United States (http://www.academickids.com/encyclopedia/index.php/United_States)
• World History (http://www.academickids.com/encyclopedia/index.php/History_of_the_world)
• Human Body (http://www.academickids.com/encyclopedia/index.php/Human_Body)
• Physical Science (http://www.academickids.com/encyclopedia/index.php/Physical_Science)
• Social Studies (http://www.academickids.com/encyclopedia/index.php/Social_Studies)
• Space and Astronomy
• Solar System (http://www.academickids.com/encyclopedia/index.php/Solar_System)