How to check current SCN ?

SQL> select timestamp_to_scn(to_timestamp('01/01/2017 00:30:00','DD/MM/YYYY HH24:MI:SS')) as scn from dual;

       SCN
----------
6.4792E+12

SQL> set numwidth 30
SQL> select timestamp_to_scn(to_timestamp('01/01/2017 00:30:00','DD/MM/YYYY HH24:MI:SS')) as scn from dual;

                           SCN
------------------------------
                 6479247526568

SQL> select scn_to_timestamp(6479247526568) from dual;

SCN_TO_TIMESTAMP(6479247526568)
---------------------------------------------------------------------------
01-JAN-17 12.29.58.000000000 AM

SQL>