The lowest prime number is TWO, which is the first and only even prime number. It is the smallest natural number that is not a unit and has no divisors other than itself and one. TWO is the only prime number that is even, and it is the only number that is both prime and even. It is also the only number that is both prime and odd. TWO is an important number in mathematics, as it is the base of the binary numeral system, which is used to represent all numbers in computers.