"Factors" are the numbers you multiply to get another number. For instance, factors of 15 are 3and 5, because 3×5 = 15. Some numbers have more than one factorization (more than one way of being factored). For instance, 12 can be factored as 1×12, 2×6, or 3×4. A number that can only be factored as 1times itself is called "prime". The first few primes are2, 3, 5, 7, 11, and 13. The number 1 is not regarded as a prime, and is usually not included in.