SQL> show version
Oracle SQLDeveloper Command-Line (SQLcl) version: 126.96.36.199 build: 188.8.131.521.1748
SQL> oerr -v
SQL> oerr ora 39826
Oerr: String to number conversion failed in Oerr
There seems to be a range of error codes between 34500 (give or take a few) and 40000 which trigger the above error.
The oerr binary from the full Oracle client returns the error details successfully:
: $ORACLE_HOME/bin/oerr ora 39826
39826, 0000, "Direct path load of view or synonym (%s.%s) could not be resolved."
// *Cause: A synonym or view could not be translated.
// *Action: Verify that the view or synonym is valid.
This is different from trying a non-existent error code:
SQL> oerr ora 1067
Oerr: No match found in Oerr.
ORA-01067 does not exist, so the above "No match" answer is correct. In any case, "String to number conversion failed in Oerr" doesn't look right.
Remark: same behaviour in SQL Developer 21.2.1.
Just thought I'd mention it...