how to check if number is prime in c code example
Example 1: program to know if a number is prime
#include
using namespace std;
bool Is_Prime(long long x){
if(x%2==0)return false;
for(int i=3;i*i<=x;i+=2)
if(x%i==0)return false;
return true;
}
int main(){
long long x;
cin>>x;
if(Is_Prime(x))cout<<"Is Prime";
else cout<<"Is not Prime";
}
Example 2: c program to check prime number using for loop
#include
int main() {
int n, i, flag = 0;
printf("Enter a positive integer: ");
scanf("%d", &n);
for (i = 2; i <= n / 2; ++i) {
// condition for non-prime
if (n % i == 0) {
flag = 1;
break;
}
}
if (n == 1) {
printf("1 is neither prime nor composite.");
}
else {
if (flag == 0)
printf("%d is a prime number.", n);
else
printf("%d is not a prime number.", n);
}
return 0;
}
Example 3: prime number c
#include
int main()
{
int i, num, p = 0;
printf("Please enter a number: \n");
scanf("%d", &num);
for(i=1; i<=num; i++)
{
if(num%i==0)
{
p++;
}
}
if(p==2)
{
printf("Entered number is %d "\
"and it is a prime number.",num);
}
else
{
printf("Entered number is %d "\
"and it is not a prime number.",num);
}
}