Pgm to find prime nos

Prime No

#include <stdio.h>
#include <string.h>
#include <math.h>

main()
{
  int primes[1000];
  primes[0]=2;
  primes[1]=3;
  int primes_len=2,is_prime,i,j,i_sqrt;
  for(i=5;i<=1000;i+=2){
      is_prime=1;
      i_sqrt=sqrt(i);
      for(j=0;j<primes_len;j++){
          if(primes[j]>i_sqrt){
              break;
          }
          if(i%primes[j]==0){
              is_prime=0;
              break;
          }
      }
      if(is_prime==1){
          primes[primes_len]=i;
          ++primes_len;
      }
  }
  for(i=0;i<primes_len;i++){
      printf("%d ",primes[i]);
  }
}