51st

The number 51 is the natural number following 50 and preceding 52. In Roman numerals, it is written as LI. In the decimal system, 51 is an odd number. It is a composite number, with its prime factorization being 3 × 17. The sum of its digits is 5 + 1 = 6.

In various contexts, the number 51 holds significance. For instance, the United States has 50 states, and the District of Columbia is sometimes referred to as the "51st state" due to its unique political status. The atomic number of antimony is 51. In sports, a jersey number of 51 might be worn by an athlete. In popular culture, the area code 51 is associated with the fictional "Area 51," a highly classified United States Air Force facility. The 51st parallel north is a line of latitude. The 51st meridian east is a line of longitude. The year 51 AD and 51 BC are also historical periods. There are 51 weeks in a standard year plus one day, or two days in a leap year. The game of dominos can involve 51 tiles. The word "fifty-one" is spelled as such.