105

105 (one hundred [and] five) is the natural number following 104 and preceding 106.

← 100 101 102 103 104 105 106 107 108 109 → List of numbers — Integers ← 100 110 120 130 140 150 160 170 180 190 →
Cardinal	one hundred [and] five
Ordinal	105th
Factorization
Divisors	3, 5, 7, 15, 21, 35
Roman numeral	CV
Binary	1101001
Hexadecimal	69

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 - 2^k 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.

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

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:

• 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.
• The prison cell where Doctor Manette lived, in Charles Dickens' A Tale of Two Cities
• The space shuttle mission STS-105
• The Orbiter Vehicle Designation for Shuttle Endeavour

References

• Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group. (1987): 134zh-yue:105

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