Find files and directories with permissions 775 / 644

[k]

Or more precisely, find files and directories with permissions other than 755 / 664:

find -type d -not -perm 755 -o -type f -not -perm 644

or find files that have at least the permissions 644 but don't have 644 as the permission bits:

find -perm -644 ! -perm 644 -type f

-type f will restrict to regular files (exclude directories) and vice-versa:

find -perm -755 ! -perm 755 -type d - to exclude files.