Most people who have little or no knowledge of the occult and esoteric claim that numerology is only a hoax, or call it "the work of the Devil". Modern scientists who promote materialism claim that it's a pseudoscience, even though Pythagoras is known to have used it.
To answer your question, it's not a divination process per se. It's considered to be a mystical science. It's based on certain mathematical patterns and can become quite complex depending on the knowledge you posses about it.