error: `itoa` was not declared in this scope

I have a sample c file called itoa.cpp as below:

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

int main ()
{
  int i;
  char buffer [33];
  printf ("Enter a number: ");
  scanf ("%d",&i);
  itoa (i,buffer,10);
  printf ("decimal: %s\n",buffer);
  return 0;
}

When i compile the above code with the below command:

gcc itoa.cpp -o itoa

i am getting this error:

[root@inhyuvelite1 u02]# gcc itoa.cpp -o itoa
itoa.cpp: In function "int main()":
itoa.cpp:10: error: "itoa" was not declared in this scope

What is wrong in this code? How to get rid of this?