Overview
Fifty is the integer 50 that follows forty-nine and precedes fifty-one. In Roman numerals it is written as L. As a round multiple of ten, 50 is commonly used to denote halves (50%) and midpoints in scales and counts. It is half of a century (100 years) and gives its name to a golden jubilee, a celebration of fifty years.
Mathematical properties
Numerically, 50 is an even composite number with prime factorization 2 × 5². It is not prime and its arithmetic structure is relatively simple, which makes it a frequent example in elementary number theory and arithmetic exercises.
50 can be expressed as the sum of two integer squares in two distinct ways: 1² + 7² and 5² + 5². The sum of its proper divisors (1 + 2 + 5 + 10 + 25) equals 43, which is less than 50; this classifies 50 as a deficient number.
History and linguistic notes
The English word "fifty" derives from Old English roots meaning "five tens". Across cultures, fifty has long been treated as a notable round figure: many calendars, counting systems, and ceremonial traditions mark 50 as an important milestone. The Roman numeral L has been used for centuries in inscriptions to represent this quantity.
Uses, examples and cultural significance
In everyday contexts 50 appears frequently: as 50% to denote one half, as a standard age milestone (the 50th birthday or golden anniversary), and in political geography (for example, the United States comprises 50 states). In chemistry, the atomic number 50 belongs to tin (Sn), a well-known metal used historically for alloys and coatings. In statistics, the 50th percentile is the median of a distribution.
Notable distinctions
Aside from its arithmetic simplicity, fifty serves as a convenient round base in measurement and communication. It often marks dividing lines (half of 100) and is widely used in lists, rankings and thresholds where a midpoint or a notable milestone is required.