48 is the natural number following 47 and preceding 49.

In mathematics

Forty-eight is the double factorial of 6, four dozens, a highly composite number, a 17-gonal number and a Harshad number.

There are 11 solutions to the equation φ(x) = 48, namely 65, 104, 105, 112, 130, 140, 144, 156, 168, 180 and 210. This is more than any integer below 48, making 48 a highly totient number.

In science

• The atomic number of cadmium
• The number of Ptolemaic constellations

In astronomy,

Messier object M48, a magnitude 5.5 open cluster in the constellation Hydra

The New General Catalogue object (http://www.ngcic.org/) NGC 48, a barred spiral galaxy in the constellation Andromeda

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros1-175.html) of the solar eclipse series which began on -1331 February 8 and ended on -15 April 9. The duration of Saros series 48 was 1316.2 years, and it contained 74 solar eclipses.

The Saros number (http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1-175.html) of the lunar eclipse series which began on -1246 July 11 and ended on 124 October 11. The duration of Saros series 48 was 1370.3 years, and it contained 77 lunar eclipses.

In other fields

Forty-eight is also:

• twice the total number of major and minor keys in the Western tonal music (twenty-four), not counting enharmonic equivalents. Johann Sebastian Bach's Well-Tempered Clavier is informally known as The Forty-Eight because it consists of a prelude and a fugue in each major and minor key, for a total of forty-eight pieces.
• the code for international direct dial phone calls to Poland.
• the model number of the HP-48 S/SX/G/GX/G+/GII
• the number of hours in two days, and hence also part of the title of the movies 48 Hrs. and Another 48 Hrs., starring Eddie Murphy and Nick Nolte.
• the years AD 48, 48 BC, or 1948.