Escape the second - in --number.
Add a --version option, to print just version information.

Also, use #defines starting at 128 (outside the ASCII range) for long
options having no short-option equivalent, and have -h/--help exit with
an exit status of 0 (you just asked for usage information, and you got
it - no fault, no error).
Add --version to the usage message.
Document --version.