49 is the natural number following 48 and preceding 50.

Cardinal	forty-nine
Ordinal	49th (forty-ninth)
Factorization
Roman numeral	XLIX
Binary	0110001
Hexadecimal	31

In mathematics

Forty-nine is a square number, a centered octagonal number, and a Somer pseudoprime based on 8.

In science

• The atomic number of indium

In astronomy,

Messier object M49, a magnitude 10.0 galaxy in the constellation Virgo.

The New General Catalogue object NGC 49 , a spiral galaxy in the constellation Cetus.

The Saros number of the solar eclipse series which began on -1248 February 22 and ended on 32 March 29. The duration of Saros series 49 was 1280.1 years, and it contained 72 solar eclipses.

The Saros number of the lunar eclipse series which began on -1217 June 21 and ended on 81 August 8. The duration of Saros series 49 was 1298.1 years, and it contained 73 lunar eclipses.

In other fields

Forty-nine is also:

• The span between Jubilee years as ordained in the Holy Bible.
• The number of strings on a harp and the number of keys on a celesta.
• I-49 is the designation for a US interstate highway in Louisiana.
• The code for international direct dial phone calls to Germany.
• As in 49er, the moniker of those who participated in the 1849 California Gold Rush.
• In the title of Thomas Pynchon's novel The Crying of Lot 49.
• In the title of the movie Ladder 49.
• The year AD 49, 49 BC, and 1949.
• The car number of the BAM Racing Schwan's Home Service Dodge Charger, currently driven by NASCAR veteran Ken Schrader.