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chmod 664 (rw-rw-r--)

The owner and group can read and write, and others can read. The default for new files when the umask is 002.

Who can do what

Commands

chmod 664 my-file
# same thing in symbolic form:
chmod u=rw,g=rw,o=r my-file

In ls -l output, a file with this mode shows as -rw-rw-r-- and a directory as drw-rw-r--.

Try a different mode