And to conclude this section, we finally take a look at the elusive first digit of a numeric mode. As you can see, this first digit is used for setting the sticky, suid and sgid bits:

Here's an example of how to use a 4-digit numeric mode to set permissions for a directory that will be used by a workgroup:

# chmod 1775 /home/groupfiles

As homework, figure out what the meaning of the 1755 numeric permissions setting. :)