int isPrime(long long number) {
if (number == 0 || number == 1 || (number % 2 == 0 && number > 2)) {
return 0;
}
else {
for (long long i=3; i <= (long long)sqrt(number)+1; i++) {
if (number % i == 0) {
return 0;
}
}
return 1;
}
}#include <stdio.h>
main() {
int n, i, c = 0;
printf("Enter any number n:");
scanf("%d", &n);
//logic
for (i = 1; i <= n; i++) {
if (n % i == 0) {
c++;
}
}
if (c == 2) {
printf("n is a Prime number");
}
else {
printf("n is not a Prime number");
}
return 0;
}
Program Output:#include <stdio.h>
int main() {
int n, i, flag = 0;
printf("Enter a positive integer: ");
scanf("%d", &n);
if (n == 0 || n == 1)
flag = 1;
for (i = 2; i <= n / 2; ++i) {
if (n % i == 0) {
flag = 1;
break;
}
}
// flag is 0 for prime numbers
if (flag == 0)
printf("%d is a prime number.", n);
else
printf("%d is not a prime number.", n);
return 0;
}#include <stdio.h>
void main() {
int number;
printf("\n\n\tEnter the number and we will check, if the number is prime or not : ");
scanf("%d", &number);
if (number == 0 || number == 1 || (number % 2 == 0 && number > 2))
{
printf("\n\tThe entered number is not a prime number!");
}
else
{
printf("\n\tThe entered number is a prime number!");
}
}