How find input number is prime number in c plus plus?

Answer 1

#include
#include

bool is_prime (const unsigned num)
{
if (num<2U) return false;
if ((num&1U)==0U) return num==2U;
const unsigned max {static_cast(std::sqrt (static_cast(num))) +1U};
for (unsigned div {3U}; divif ((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";
}