800

800 is a natural number that follows 799 and precedes 801. In decimal notation it is written as 800. In Roman numerals it is DCCC.

Mathematically, 800 factors as 2^5 × 5^2. It has 18 positive divisors: 1, 2, 4, 5, 8, 10, 16, 20, 25, 32, 40, 50, 80, 100, 160, 200, 400, and 800. The sum of its proper divisors is 1153, which exceeds 800, so 800 is an abundant number. It is also a Harshad (Niven) number in base 10, since 800 is divisible by the sum of its digits (8). Representations in other bases include binary 1100100000_2, hexadecimal 0x320, and octal 0o1440.

In broader use, 800 appears in several contexts. The year 800 CE is noted in European history for Charlemagne’s coronation as Holy Roman Emperor. In athletics, the 800 metres is a standard middle-distance track event. In telecommunications, the prefix 800 is used for toll-free numbers in North America, and internationally the +800 code designates the international toll-free service.