217

217, or two hundred seventeen, is a natural number that comes after 216 and before 218. It is used in various numbering schemes and appears in different mathematical and cultural contexts.

In mathematics, 217 is a semiprime, being the product of the primes 7 and 31. It is therefore not a prime and has divisors 1, 7, 31, and 217. The digit sum of 217 is 10, and it is not a perfect power.

In Roman numerals, 217 is written as CCXVII.

As a calendar year, 217 CE falls within the period of the Roman Empire. It is noted for the assassination of Emperor Caracalla and the subsequent accession of his successor, Macrinus.

In geography and infrastructure, 217 is used as an area code for central Illinois, including Springfield and Champaign–Urbana. There are highways and routes designated with the number 217 in various jurisdictions, reflecting its role in transportation nomenclature.

In astronomy, 217 Eudora is a main-belt asteroid. It is one of many minor planets that bear numerical designations corresponding to their order of discovery.

Beyond these uses, 217 appears in a range of miscellaneous codes, model numbers, and street or building identifiers, illustrating how numbers function as practical labels across different domains.