"Eighteen" is a number that follows seventeen and precedes nineteen. It is often associated with the age when individuals reach legal adulthood in many countries, allowing them to vote, sign contracts, and make independent decisions. The number is also significant in various cultures and traditions, often marking a transition into adulthood. In mathematics, eighteen is an even number and can be expressed as the product of two prime numbers: 2 and 3. It is also the sum of the first three prime numbers: 2, 3, and 5. In Roman numerals, eighteen is represented as XVIII.