Eighteen is a composite number, its proper divisors being 1, 2, 3, 6 and 9.
18 is the age limit for being allowed a driver's license in many parts of the world.
... of which 36.4% have children under the age of 18 living with them, 65.1% are married couples living together, 8.7% have a female householder with no husband present, and ...