855

855 is the natural number that comes after 854 and before 856. In Roman numerals, it is written as DCCCLV.

In mathematics, 855 factors as 3^2 × 5 × 19. The positive divisors are 1, 3, 5, 9, 15, 19, 45, 57, 95, 171, 285, and 855. The sum of its proper divisors (excluding 855) is 705, which means 855 is a deficient number.

Representations of 855 include binary 1101010111, octal 1527, and hexadecimal 0x357.

As a year, 855 CE falls in the 9th century. Historical records from that period vary by region, but the era is associated with events across medieval Europe and surrounding areas, including interactions among emerging kingdoms and distant cultural exchanges.

In telecommunications, 855 is a toll-free dialing prefix used in the North American Numbering Plan. It is among several toll-free prefixes such as 800, 888, 877, 866, 844, and 833, and is assigned to numbers that allow callers to reach services without paying a per-call charge. Toll-free numbers are widely used for customer service, technical support, and information hotlines.