How to find current SCN number from Oracle database?

How to find current SCN number from Oracle database?

col current_scn for 99999999999999999

select current_scn from v$database;

select to_char(current_scn) from v$database;

select current_scn from v$database;

select min(checkpoint_change#) from v$datafile_header where file# not in (select file# from v$datafile where enabled = 'READ ONLY');