htaccess 666 permission – security risk?

Following admin prompt and Codex, I gave .htaccess file a 666 permission so that I could set custom permalinks.

But I can’t find clarification as to whether I have to keep it at 666 permission after I set my custom permalink structure, or can lower it to something which seems more secure (i.e. not publicly writable)

Or, is there some other hack one uses to keep it secure?