109

109 is a natural number that follows 108 and precedes 110. It is an odd prime number, the 29th prime in the sequence of primes. In decimal notation it is written as 109; in Roman numerals it is CIX. The sum of its digits is 10, giving a digital root of 1. In common numeral systems, it can be represented as binary 1101101, hexadecimal 6D, and octal 155. In ASCII, decimal 109 corresponds to the lowercase letter 'm'.

Meitnerium (Mt), element 109, is a synthetic superheavy element named after Lise Meitner. It was first synthesized in 1982 by a research team at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. Meitnerium has no stable isotopes and exists only for fractions of a second to a few minutes under laboratory conditions, making detailed chemical studies difficult.

Messier 109 (M109) is a spiral galaxy in the constellation Ursa Major. It was discovered by Pierre Méchain and catalogued by Charles Messier in 1789. M109 is a distant object observed in light from billions of years ago and is studied as part of broader surveys of spiral galaxies.

As a calendar year, 109 CE occurred during the early second century; it is referenced in historical records relating to the Roman Empire and other regions of the time.

Other uses of the number 109 include its use as an index or designation in road numbering, literature, and cataloging systems, where 109 appears as a label or identifier in various national or organizational schemes.