55 (number)

55 is the natural number following 54 and preceding 56.

List of numbers — Integers << 50 51 52 53 54 55 56 57 58 59 >>
Cardinal	fifty-five
Ordinal	55th (fifty-fifth)
Factorization	<math>5\cdot 11<math>
Roman numeral	LV
Binary	110111
Hexadecimal	37

Mathematics

Fifty-five is a heptagonal number and a triangular number, made up of the numbers 1 to 10 added up, and it is also the sum of the squares of the integers 1 to 5. It is also a Fibonacci number (the largest Fibonacci number to also be a triangular number) and a Kaprekar number.

Other fields

Fifty-five is also:

• The atomic number of caesium.
• The number of delegates who attended the Constitutional Convention.
• In gallons, a common size of drum containing liquids.
• In miles per hour in many states of the United States, a common speed limit; it was the national speed limit for a time during the energy crisis of the late 1970s.
• In years of marriage, the emerald wedding anniversary.
• The code for international direct dial phone calls to Brazil.
• The designation of United States Interstate 55, a freeway that runs from Louisiana to Illinois.
• The year AD 55, 55 BC, or 1955.