According to a networking utility I’m using, all of the below are considered common ports. Avoid using them unless you must (e.g. 25, 80, 443).
1, 7, 20, 21, 22, 23, 25, 42, 43, 53, 69, 79, 80, 88, 106, 110, 111, 113, 115, 119, 123, 135, 137, 138, 139, 143, 161, 177, 194, 311, 379, 389, 427...