I get a call almost everyday from this number and they never leave a voicemail...I don't answer numbers I don't know.  Anyone know who this is?

I get calls from this number too, I answer and I wait for them to say something and they say nothing and hang up, this number is irritating me for I don't know if it's needed or not. I get call by this number almost 2 or three times a day and they call me during night and school. I'm blocking this number