Google free reverse telephone number lookup, go to the site, enter the number, etc. If there is no answer and it's important, you can try intellius, an information broker site. They charge $4.99 per phone number lookup. They take up to 24(or 48) hours to do their search. If no results, they don't charge.

Does this have to do with spammers calling your house? There is something called telephone number spoofing. I had one of those drug-selling people call my house yet again. Later I called the number back, only to find it legitimately belonged to a Verizon conference center. The Verizon rep told me about number spoofing, so the number on your phone may not be the actual call number.