executing function on SQL prompt

[pando]

lsc@DEV817-ES7J2BKT8ZM0YY>create or replace function mynumber
  2  return number
  3  as
  4    l_number number;
  5  begin
  6    select 1
  7      into l_number
  8      from dual;
  9    return l_number;
 10  end;
 11  /

Function created.

lsc@DEV817-ES7J2BKT8ZM0YY>variable x number
lsc@DEV817-ES7J2BKT8ZM0YY>exec :x:=mynumber

PL/SQL procedure successfully completed.

lsc@DEV817-ES7J2BKT8ZM0YY>print x

         X
----------
         1