105 (number)
From Wikipedia, the free encyclopedia
105 (one hundred [and] five) is the natural number following 104 and preceding 106.
| Cardinal | one hundred [and] five |
| Ordinal | 105th |
| Factorization |  |
| Divisors | 3, 5, 7, 15, 21, 35 |
| Roman numeral | CV |
| Binary | 1101001 |
| Hexadecimal | 69 |
[edit] In mathematics
105 is the double factorial of 7. 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. The distinct prime factors of 105 add up to 15, and so do the ones of 104, hence the two numbers form a Ruth-Aaron pair under the first definition.
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.)
105 is the sum of the first five square pyramidal numbers.
[edit] In science
- The atomic number of hahnium, also known as dubnium.
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
- 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.
[edit] In other fields
105 is also:
- The designation of some spur routes of Interstate 5.
- A film format introduced by Kodak for their first folding camera. See 120 film.
- The name of a song by the band Smash Mouth.
- The name of a road bicycle groupset from Shimano.
- The number of surat al-Fil in the Qur'an.
- The year AD 105 or 105 BC.
