The number 691 is an integer that follows 690 and precedes 692. It is an odd number and can be expressed as the sum of two prime numbers, specifically 347 and 344. In mathematics, it is classified as a composite number, meaning it has divisors other than one and itself. In terms of its properties, 691 can be factored into 1, 7, 13, 53, 91, 691. It is also notable in various contexts, such as in area codes or postal codes, where it may represent specific regions or services.