I want to create a random number, store the digits of the random number into an array, then store the array into a string

I want to create a random number, store the digits of the random number into an array, then store the array into a string. I am trying to hide the digits from the user. This is what I have, it is only storing two numbers. How can i fix this or do it differently so it works?

int random,n,digit;

srand(time(NULL)); random = (rand() % 9999)+1000;

        n= random;

        char a[11];
        int i = 0;
        while (n > 0) {
        long int digit = n % 10;
        a[i] = digit;
        ++i;
        n /= 10;
        }
        a[i] = '\0';

        

        cout << digit << endl;

        string hiddenNumber(to_string(digit).length(),'-');

'''