set numwidth 50
select 1000*60*60*24*365 lots_of_sequences_per_year from dual;

select to_number(lpad(9,38,9)) a_really_big_integer from dual;

select trunc(to_number(lpad(9,38,9))/31536000000) how_long_is_forever from dual;

SQL> select * from v$version;

BANNER
---------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.7.0 - 64bit Production

SQL> set numwidth 50
SQL> select 1000*60*60*24*365 lots_of_sequences_per_year from dual;

                        LOTS_OF_SEQUENCES_PER_YEAR
--------------------------------------------------
                                       31536000000

1 row selected.

SQL> 
SQL> select to_number(lpad(9,38,9)) a_really_big_integer from dual;

                              A_REALLY_BIG_INTEGER
--------------------------------------------------
            99999999999999999999999999999999999999

1 row selected.

SQL> 
SQL> select trunc(to_number(lpad(9,38,9))/31536000000) how_long_is_forever from dual;

                               HOW_LONG_IS_FOREVER
--------------------------------------------------
                      3170979198376458650431253170

1 row selected.

SQL> 

SQL> select power(10,39)/(365.2425*24*60*60*1000) from dual;
POWER(10,39)/(365.2425*24*60*60*1000)
-------------------------------------
        31688738506811430964562103463

1 row selected.