29 (twenty-nine) is the natural number following 28 and preceding 30.

Cardinal	twenty-nine
Ordinal	twenty-ninth
Factorization	prime
Roman numeral	XXIX
Binary	11101
Hexadecimal	1D

In mathematics

It is the tenth prime number, and also a primorial prime, the next prime number as well as primoral prime being thirty-one, with which it comprises a twin prime. Twenty-nine is also a Sophie Germain prime. It is also the sum of three squares, 2² + 3² + 4². It is a Lucas number, a Pell number and a tetranacci number.

None of the first 29 natural numbers have more than two different prime factors. This is the longest such consecutive sequence.

In science

• The atomic number of copper

In astronomy,

Messier object M29, a magnitude 9.0 open cluster in the constellation Cygnus

The New General Catalogue object NGC 29 , a spiral galaxy in the constellation Andromeda

The Saros number of the solar eclipse series which began on -1881 March 1 and ended on -583 April 19. The duration of Saros series 29 was 1298.1 years, and it contained 73 solar eclipses.

The Saros number of the lunar eclipse series which began on -1814 July 21 and ended on -317 January 5. The duration of Saros series 29 was 1496.5 years, and it contained 84 lunar eclipses.

The lunar month is very close to twenty-nine days.

In other fields

Twenty-nine is:

• The number of bones in a normal human skull.
• The number of days February has on leap years.
• The number of letters in the Finnish and Norwegian alphabets.
• The designation of Interstate 29, a freeway that runs from Missouri to North Dakota.
• In the name of the town Twentynine Palms, California, also the name of the adjoining Marine Corps base, affectionately referred to by Marines as "Twentynine Stumps".
• The number of suras in the Qur'an that begin with muqatta'at
• Historical years: 29 A.D., 29 B.C., or 1929