The number 191 is an integer that follows 190 and precedes 192. It is an odd number and can be classified as a prime number, meaning it has no positive divisors other than 1 and itself. In mathematics, prime numbers are significant because they are the building blocks of whole numbers. In terms of its representation, 191 can be expressed in various numeral systems. For example, in binary, it is written as 10111111. Additionally, in Roman numerals, it is represented as CXCIV. The number also appears in various contexts, such as in area codes or as a reference in literature and history.