in the command line :
I type :
ls -i tomcat-users.xml
response:
193382 tomcat-users.xml

what this number the meaning?

Why not is -rw-r--r-- 1 ?

And when I type :
sudo chmod +w tomcat-users.xml
no response.
then I type:
vi tomcat-users.xml
then type :
a
the worning is:
10: Warning: Changing a readonly file

I am surprised.
how to view and change document right?