Should be 12345 but sometimes it don’t work even after factory reset.

Following the following YouTube guide.

Note: I discovered mine was actually 6 digits long so when he edits the JohnTheRipper ini to only scan for 5 digits you might want to skip that and leave it at min 1 digit and max 8.

Also because of what JohnTheRipper is, you’re AV software might flag it falsely as not safe.

N900 unlock

EDIT- Might as well do 1 to 10 in the johntheripper ini file as 10 is the max and maybe what the code was set to.  And as it’s only digits won’t take too long.