Straightforward implementation in C using standard library functions, inspired by the strlen in the other C answer.
Number of characters: 57
p(char*s){char*r=strdup(s);strrev(r);return strcmp(r,s);}
Confession: I'm being the bad guy by not freeing r here. My current attempt at being good:
p(char*s){char*r=strdup(s);s[0]=strcmp(strrev(r),s);free(r);return s[0];}
brings it to 73 characters; I'm thinking of any ways to do it shorter.