What is the smallest prime number?
The smallest prime number is 2. It is also the only even prime number, because every other even number can be divided by 2.
A prime number has exactly two different factors: 1 and itself. The number 2 can be divided only by 1 and 2, so it is prime. The number 1 is not prime because it has only one factor.
Every even number greater than 2 can be divided by 2, so it has at least three factors and is composite. That makes 2 unique among the primes. All other primes are odd: 3, 5, 7, 11 and so on.
An unsolved puzzle
In 1742, mathematician Christian Goldbach suggested that every even number greater than 2 is the sum of two primes, such as 10 = 3 + 7. Computers have checked this for enormous numbers, but no one has ever proved it is always true.
Did You Know?
The number 2 is also the base of the binary system that computers use, in which every number is written with only 0s and 1s.