C program to find next prime palindrome
C program to find next prime palindrome: In this code user will enter
a number(say n) and we have to find a number greater than n which is
a palindrome as well as prime. For example if the input is 7 then output
will be 11 as it is prime as well as palindrome, if input is 21 then
output will be 101. In our code we first check if a number is
palindrome and then check if it is prime as it will take less time as
primes occur more frequently then palindromes.
C programming code
#include <stdio.h>
#include <math.h>
#define TRUE 1
int main()
{
long n, t, r = 0, c, d;
printf("Enter an integer\n");
scanf("%ld", &n); /* n must be a natural number */
while (TRUE)
{
n++;
t = n;
/* Calculating reverse of number */
while(t)
{
r *= 10; /* Compound assignment operator r*=10 => r=r*10 */
r += t%10;
t /= 10;
}
/* if reverse equals original then it is palindrome */
if (r == n)
{
d = (int)sqrt(n);
/* Checking prime */
for (c = 2; c <= d; c++)
{
if (n%c == 0)
break;
}
if (c == d+1)
break;
}
r = 0;
}
printf("%ld\n",n);
return 0;
}
