312

312 is a natural number that follows 311 and precedes 313. It is an even composite number with prime factorization 2^3 × 3 × 13. It has 16 positive divisors. In base representations, it is 100111000 in binary, 0x138 in hexadecimal, and CCCXII in Roman numerals. The sum of its digits is 6, and it is divisible by 3 and by 6.

In mathematics, 312 is a Harshad number in base 10 since it is divisible by the sum of its digits. It is not prime, not a perfect square, and not a triangular number. It can be expressed as 24 × 13 and as 2^3 × 3 × 13.

Historically, the year 312 CE (AD 312) is notable for the Battle of the Milvian Bridge, where Constantine the Great defeated Maxentius. This victory helped shape the course of the Roman Empire and is associated with Constantine’s eventual embrace of Christianity; the Edict of Milan, which granted tolerance to Christians, followed in 313 CE.

In modern usage, 312 is the area code associated with downtown Chicago, Illinois. It originated as one of the original North American area codes in the mid-20th century and remains closely linked to the city in popular usage.