Pay attention to the length of the room. If it consists of 4-5 figures, then, belongs to one of the companies or the person who provide certain services. Try to "break" this combination using Internet search engines to get to know the person or company by phone number for free. You will learn whether you can trust this number, or it belongs to fraud, for example, through the reviews of other customers and Internet users.
Look at the first three digits after the international code, if it is 9-10 digits. In them you can find out what the mobile operator and what country, region or city was the current phone. It considerably will narrow a circle of searches and you'll be able to contact one of the local shops to learn about a person by number. Remember that the experts will provide information on the owner only in case of emergency, for example if you want to pass the phone to the owner, or become a victim of scammers using this number.
Be sure to follow the procedure to search through available Internet search engines by typing in the string you are interested in the room completely. If you are aware of at least the minimum information about the owner (name, surname, city of residence, company, etc.), include them too. You can also select some time frame for the search, for example, for the current year. The chances to find a person by phone number in this way is small, but with more options it increased. In this case you'll be lucky if people leave your number on any website.
Try to know a person through phone number for free using sites, programs and services, which would provide for a mandatory input of personal data: Skype, ICQ, some social networks, email clients, etc. to appeal to people who may know the owner, as well as to the administration of sites on which it is registered. Finally, you can just call on the desired phone and communicate with the owner directly, but this should be done only when you are sure that you will not become a victim of fraud.