HOW TO GIVE A DEFAULT TO A TRULY INTERACTIVE FUNCTION

[gnuist006@hotmail.com (gnuist006)]

(defun demo (&optional number)
"Demo of an     optional argument of the function."
(interactive "nEnter a number:")
(setq defaultval 5)
(if (null number) (setq number defaultval))
(insert (format "%s" number))
)                                        (demo)                       
           ; works due to optional argument

I want the default to work on the command line also.
They say emacs is customizable. OK it is if you only want to do what
it
can do, and never try to do what you want to do.

I want to invoke it on command line ie M-x demo
It comes and says
Enter a number:_

I prefer it display the default 5 in the message and there is
SINGLE instance of 5 in the function. ie using defaultval.

If this cannot do this and you were all lying to yourself that
emacs is customizable, infinitely extensible, then I atleast want
quick fix for this.

When I hit RTN after it begs for number once, it go away and use
defaultval and stop buggin me.

At present it does not stap and keeps bugging till I enter 5.
Why do I have to remember the default when I am giving it that much
money?