prime (prim) n.[ME, fr. MF, fem. of prin first, L primus; akin to L prior] 1 :first in time: original 2 a : having no factor except itself and one (3 is a number) b : having no common factor except one ( 12 and 25 are relatively ) 3 a : first in rank, authority or significance : principal b : having the highest quality or value ( television time) [from Webster's New Collegiate Dictionary]
A prime number is any number with no divisors other than itself and 1, such as 2 and 11. Any number can be written as a product of prime numbers in a unique way (except for the order).