SQL & PL/SQL

Hello,
I want to convert the raw datatype number to number datatype.

for ex:- I have number 40 then i want to convert it to raw or else from a raw value ( ex:- 33FFE is raw value for 40) then i should pass this value to a function and i should get a number value i,e 40. I am using a built in oracle package for the same. dbms_xdbutl_int.rawtonum() for the same it also does the conversion but the problem is with negative value. When i pass -40 ( negative 40) it gives a invalid answer.

*Please guide me with some proper method in which i can pass a raw value , either positive or negative to the function and then get a number in return , with proper sign ( +ve or -ve).*

thanks in advance !!!!