**54** (**fifty-four**) is the natural number following 53 and preceding 55.

**54** is a 19-gonal number. Twice the third power of three, 54 is a Leyland number. 54 can be written as the sum of three squares in three different ways: 7^{2} + 2^{2} + 1^{2} = 6^{2} + 3^{2} + 3^{2} = 5^{2} + 5^{2} + 2^{2} = 54. It is the smallest number with this property. Like all other multiples of 6, it is a semiperfect number.

In base 10, 54 is a Harshad number.

The Holt graph has 54 edges.

The sine of an angle of 54 degrees is half the golden ratio.

The factorial of 54 is 7071230843697339241♠230843697339241380472092742683027581083278564571807941132288000000000000, or approximately 7071230843697339241♠2.30843697339241×10^{71}.

The atomic number of xenon is 54.
Messier object M54, a magnitude 8.5 globular cluster in the constellation Sagittarius
The New General Catalogue object NGC 54, a spiral galaxy in the constellation Cetus
The number of years in three Saros cycles of eclipses of the sun and moon is known as a **Triple Saros** or *exeligmos* (*Greek*: "turn of the wheel").
The Saros number of the solar eclipse series which began on 25 July 1285 BC and ended in September of AD 32. The duration of Saros series 54 was 1316.2 years, and it contained 74 solar eclipses.
The Saros number of the lunar eclipse series which began on -964 May 14 and ended on 334 July. The duration of Saros series 54 was 1298.1 years, and it contained 73 lunar eclipses.
Fewest points in an NBA playoff game: Chicago (96), Utah (54), June 7, 1998
The New York Rangers won the Stanley Cup in 1994, 54 years after their previous Cup win. It is the longest drought in the trophy's history.
For years car number 54 was driven by NASCAR's Lennie Pond. More recently, it is known as the Nationwide Series car number for Kyle Busch.
A score of 54 in golf is colloquially referred to as a perfect round. This score has never been achieved in competition.
The number used when a player is defeated 3 games in a row in racquetball.

**54** is also:

The number of milligrams of caffeine in 12 ounces of Mountain Dew.
+54 The code for international direct dial phone calls to Argentina
Municipal Okrug 54, a municipal okrug of Nevsky District of Saint Petersburg, Russia
A broadcast television channel number
*54*, a 1998 film about Studio 54 starring Ryan Phillippe, Mike Myers, and Salma Hayek
*54*, a novel by the Wu Ming collective of authors
In the title of a 1960s television show *Car 54, Where Are You?*
The number of the French department Meurthe-et-Moselle
New York's Warwick New York Hotel is on West 54th Street
The number of cards in a deck of playing cards, if two jokers are included
The number of countries in Africa
Year identifier used on motor vehicles registered in the UK between 1 September 2004 and 28 February 2005
Six by nine, the incorrect Answer to the Ultimate Question of Life, the Universe, and Everything