687

687 is the natural number that comes after 686 and before 688. In mathematics, it is an odd composite number. Its prime factorization is 3 × 229; both 3 and 229 are prime, making 687 the product of two distinct primes, i.e., a squarefree semiprime. Its positive divisors are 1, 3, 229, and 687.

In various numeral systems, 687 is represented as 1010101111 in binary, 1257 in base-8, and 2AF in hexadecimal. In Roman numerals, it is DCLXXXVII.

As a calendar year, 687 can refer to the year 687 CE or 687 BCE, depending on era conventions. The historical events associated with these years depend on regional sources and scholarly interpretation.

In other uses, 687 may appear as a designation, model number, or code in catalogs and systems, but such uses are not standardized.