/*

 * name: EsPrimo

 * @param (unsigned long long)

 * @return (bool)(true == es primo) 

 */

bool EsPrimo(unsigned long long n)

{

	// Declaración de 55 primos para una más rapida comprobación.

	const unsigned int primes55[] = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,

    73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,

    181,191,193,197,199,211,223,227,229,233,239,241,251,257};

    

    for(unsigned int i=0;i<55;i++) {

        if (n%primes55[i] == 0) {

            if (n == primes55[i]) {

                return true;

			}

            else {

                return false;

			}

		}

	}

    unsigned int maxtest = (long)sqrt(n); // Mas eficiente que x>>4 (x/(2^4)).

    for(unsigned int i=259; i<maxtest; i+=2) {

        if (n%i == 0) {

            return false;

		}

	}

    return true;

}