A first-rate quantity is a constructive integer better than 1 that has no constructive divisors aside from 1 and itself. As an illustration, is 7 a primary quantity? The reply is sure, since 7 solely has two constructive divisors: 1 and seven.
Figuring out whether or not a quantity is prime has sensible functions, together with cryptography, laptop science, and arithmetic. One of many first vital historic developments in prime quantity principle was Euclid’s proof that there are infinitely many prime numbers.