123      ;; decimal           all Emacs
#b101    ;; binary            Emacs 21 up, XEmacs 21
#o77     ;; octal             Emacs 21 up, XEmacs 21
#xFF     ;; hex               Emacs 21 up, XEmacs 21
#3r210   ;; any radix 2-36    Emacs 21 up (but not XEmacs 21.4)