If you want to find out who's been calling you and all you have is the phone number, take advantage of several ways to go about finding the information. The easiest is to perform a reverse phone number look-up through an online phone directory. Just enter a phone number to learn the owner's name and address. You can also try typing the number into a free search engine like Google.

Head over to Whitepages.com and click on the "reverse phone" tab. Type in the full 10-digit number and hit "search." If the number is listed, the website will tell you who it's registered to. Other sites, including Intelius, Zabasearch and Anywho.com offer the same service. Some claim to correlate utility bills and public records, so it's worth trying multiple websites to see what comes back. Reverse phone look-ups are both free and paid. Generally, it's free for landline phone numbers, but you'll have to pay to find the owner of a cellphone.

Just typing the 10-digit phone number into Google's search bar can throw up some favorable results. If the number belongs to a business, for example, then you'll usually get a match within the first four or five search results. A private landline or cellphone number might show up on Google, too, if the owner has put her number somewhere on the web, such as on a personal blog site or social media account. It's also worth it to open Facebook and type the phone number in the search bar at the top of the screen. If someone has linked the phone number to his Facebook profile, then you should score a direct hit in the search result.

Pipl is another site that will match a number to a name. Instead of scouring phone directories, Pipl searches the "deep web," or webpages that don't reveal themselves to common search engines such as databases, registration-required forums and sites that are password protected. In theory, it should pick up landline and cellphone numbers that people have posted on hard-to-access places like Facebook walls. Just type the phone number, including the area code, into the search bar and see what comes back. Pipl displays a photo alongside the search result, so it's a good choice if you think you know the owner and are looking to verify that you have found the right name.

For an offline version of a reverse phone number look-up, head to your local library and ask to use a cross reference phone directory such as Criss+Cross. Whereas a regular phone directory uses the owner's name and location to categorize telephone numbers, a cross reference phone directory lets you look up phone numbers in order to locate a name and address. Numbers are listed numerically starting with the area code, and you'll need to know what area you're searching so you can look in the right directory. Use an online area code locator to find the city associated with the area code. For example, area code 215 means you should look in the directory for Philadelphia and Levittown in Pennsylvania.