251

251 is a natural number that comes after 250 and before 252. It is the 251st positive integer.

In mathematics, 251 is prime. It is also a Sophie Germain prime, since 2 times 251 plus 1 equals 503, which is prime. This makes 251 part of a class of primes used in certain number theory discussions and cryptographic examples.

Its binary representation is 11111011, and its hexadecimal representation is FB. In Roman numerals, 251 is written as CCLI.

The year 251 CE is associated with the outbreak of the Cyprian plague in the Roman Empire, a major epidemic that affected parts of Europe and the Mediterranean in the mid-3rd century.

In the United States, 251 is an area code serving southwestern Alabama, including Mobile and nearby communities.

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