CCCXVII

CCCXVII is the Roman numeral representation of the integer three hundred seventeen. The number 317 is an odd, prime number, as it is not divisible by any prime smaller than its square root (approximately 17.8). It is also a part of the sequence of prime numbers that begins 2, 3, 5, 7, 11, and so on. In base‑10, the digits 3, 1, and 7 sum to 11, and the product of the digits equals 21.

In historical chronology, the year 317 CE falls within the period of the late Roman Empire. It is contemporaneous with the reign of Emperor Constantine I and the early phase of the reign of his son Constantine II. In the Christian church, 317 CE is marked by the Synod of Seleucia‑Onomera, a council not to be confused with the later and more well‑known First Council of Nicaea (325 CE). Contemporary civil and ecclesiastical documents from the period occasionally record dates using Roman numerals, and CCCXVII would denote the 317th year in such a system.

The minor planet 317 Gevaert, discovered in 1893, is designated by the numeric identifier 317. The asteroid is named after the Belgian engineer Paul Gevaert, whose work concerned meteorological instrumentation. In catalogues of astronomical objects, the designation 317 is therefore sometimes abbreviated to its Roman numeral form, CCCXVII, to indicate the same celestial body.

The numeral CCCXVII is also employed in military record‑keeping to designate units or designations that carry the ordinal number 317. For example, in World War II German Luftwaffe records a unit known as Sturzkampfgeschwader 317, a dive‑bombing squadron that operated during the conflict.