To find the httpd binary that is currently running, request all processes:
ps -ef |grep httpd
You should see, in the list, entries like:
nobody 9668 419 0 09:26:55 ? 10:00 /usr/local/apache1327/bin/httpd
Go to that directory where the httpd is running (in this case: /usr/local/apache1327/bin/)
cd /usr/local/apache1327/bin/
Execute this command:
./httpd -v
You should then see something like this.
Server version: Apache/1.3.27 (Unix) (Red-Hat/Linux)
Server built: Sep 2 2003 09:16:44