C Exercises: Check if a given number is circular prime or not

Last update on August 05 2025 12:55:53 (UTC/GMT +8 hours)

27. Circular Prime Check Variants

Write a program in C to check if a given number is circular prime or not.

Test Data
Input a Number: 1193

Sample Solution:

C Code:

# include <stdio.h>
# include <stdlib.h>
# include <stdbool.h>
# include <math.h>

int flg; // Global variable to store the flag indicating if the number is a circular prime or not

// Function to check if a number is prime
void chkPrime(long int n)
{
    long int i = n - 1; // Initialize 'i' to check divisibility of 'n'

    while (i >= 2) // Loop to check for divisibility of 'n' by numbers less than 'n'
    {
        if (n % i == 0) // If 'n' is divisible by 'i', set flag to 1 (not a prime number)
        {
            flg = 1;
        }
        i--; // Decrement 'i' to check the next number
    }
}

// Function to find all combinations of digits in the number and check for prime
void AllCombination(long int a)
{
    long int b1, c1, d1, e1, i, j, k, s1, z1, v1, x[8], y[8], m;

    b1 = a;
    i = 0;

    // Extracting digits of the number and storing in an array 'y'
    while (b1 > 0)
    {
        y[i] = b1 % 10;
        b1 = b1 / 10;
        i++;
    }

    c1 = 0;

    // Reversing the order of digits and storing in array 'x'
    for (j = i - 1; j >= 0; j--)
    {
        x[c1] = y[j];
        c1++;
    }

    m = i;

    // Generating all possible combinations of digits
    while (m > 0)
    {
        c1 = m - 1;
        d1 = i - 1;
        e1 = 0;
        s1 = 0;

        while (e1 < i)
        {
            z1 = pow(10, d1);
            v1 = z1 * x[c1 % i];
            c1++;
            d1--;
            e1++;
            s1 = s1 + v1;
        }
        m--;

        // Checking if the generated number is prime
        chkPrime(s1);
    }
}

// Main function
int main()
{
    long int num1; // Variable to store the input number

    // Printing information about the program and asking for user input
    printf("\n\n Check whether a given number is a circular prime or not: \n");
    printf(" -----------------------------------------------------------\n");
    printf(" Input a Number: ");
    scanf("%li", &num1);

    flg = 0; // Resetting flag to 0
    AllCombination(num1); // Calling function to check circular prime

    if (flg == 0)
    {
        printf(" The given number is a circular prime Number.\n"); // Printing if the number is a circular prime
    }
    else
    {
        printf(" The given number is not a circular prime Number.\n"); // Printing if the number is not a circular prime
    }

    return 0; // Returning 0 to indicate successful execution
}

Sample Output:

 Input a Number: 1193                                                                                         
 The given number is a circular prime Number.

Visual Presentation:

C programming: Check if a given number is circular prime or not.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to check if a number is a circular prime by rotating its digits and testing each rotation.
Write a C program to verify circular primes using an optimized prime-checking function.
Write a C program to list circular primes along with all their rotational variants.
Write a C program to test circular prime properties in a given range with early exit on failure.

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