The number "18" is an integer that follows 17 and precedes 19. It is an even number, meaning it can be divided by 2 without leaving a remainder. In mathematics, 18 is considered a composite number because it has divisors other than 1 and itself, specifically 1, 2, 3, 6, 9, and 18. In many cultures, turning 18 signifies the transition into adulthood. For example, in the United States, individuals gain the legal right to vote and enter into contracts at this age. Additionally, 18 is often associated with various rites of passage, such as high school graduation celebrations.