select to_number('19f','xxx') from dual;
----------------------
415

select to_number('f','xx') from dual;
-------------------
15

select to_char(123,'xx') from dual;
----
7b

select to_char(4567,'xxxx') from dual;
-----
11d7

select bin_to_num(1,1,0,1) a,bin_to_num(1,0) b from dual;

a b
----- ----------
13 2

select bin_to_num(1,1,1,0,1) from dual;

bin_to_num(1,1,1,0,1)
---------------------
29