Use two fields with different settings on Oracle

Question

I’m having a hard time: I’m trying to use a field that was created as number with a field created as NUMBER NOT NULL ENABLE.

The ID_ACESSO field was created like this:

"ID_ACESSO" NUMBER NOT NULL ENABLE

The PK_ACESSO field was created like this:

"PK_ACESSO" NUMBER, 

 select * from gsc_tbl066_ramal_telefonico a 
           left join gsc_view_tbl064_acesso b 
                on a.PK_ACESSO = b.ID_ACESSO;

When run gives error:

ORA-01722: invalid number 01722. 00000 - "invalid number" *Cause: The specified number was invalid. *Action: Specify a Valid number.