There is no way for you to view a number if it shows up as private.
If the caller is harassing you, calling and hanging up, being threatening, etc., you can contact your service provider/carrier and have them look into it.
Your phone should have (although some don't) the option to block private calls or unknown numbers. Just note unknown number blocking will block all numbers not in your contacts. In either case, it will often still allow the number to leave you a voice mail. Or, again, you can talk to your carrier/service provider and see if they can block private numbers from their end.