105 (number)

105 is the natural number following 104 and preceding 106. It is the double factorial of 7.

In mathematics

One hundred five is a triangular number and a dodecagonal 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 odds less than a thousand are 15, 195 and 825.

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.)

In other fields

One hundred five is also:

• The atomic number of hahnium, also known as dubnium.
• The designation of some spur routes of Interstate 5.
• A film format introduced by Kodak for their first folding camera. See 120_film.
• The year AD 105 or 105 BC.

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