Learn about prime numbers

7 can only be divided evenly by 1 or itself, so 7 is a Prime Number. Find out more in this list of prime numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127. Eratosthenes (275-194 B.C., Greece) devised a ‘sieve’ to discover prime numbers. A sieve is like a strainer that you use to drain spaghetti when it is done cooking. Eratosthenes’s sieve drains out composite numbers and leaves prime numbers behind.
The number one is far more special than a prime! It is the unit (the building block) of the positive integers, hence the only integer which merits its own existence axiom in Peano’s axioms. It is the only multiplicative identity (1.a = a.1 = a for all numbers a). A popular encryption scheme uses prime numbers to create a very good level of security (but one that may erode in the future because of a new kind of computer).