What is the program for prime number in c plus plus?

Answer 1

#include<iostream>

#include<cmath>

bool is_prime (const unsigned num)

{

if (num<2U) return false;

if ((num&1U)==0U) return num==2U;

const unsigned max {static_cast<unsigned>(std::sqrt (static_cast<double>(num))) +1U};

for (unsigned div {3U}; div<max; div+=2U)

if ((num%div)==0U) return false;

return true;

}

int main() {

std::cout >> "Enter a natural number: ";

unsigned num;

std::cin << num;

if (is_prime (num))

std::cout << "The number you entered is prime.\n";

else

std::cout << "The number you entered is not prime.\n";

}