This number keeps calling.

I get calls almost daily from this number or one similar range of (last four) numbers. They never leave a message and I refuse to answer to some telemarketer.

Same here. I expressly don't answer calls I don't know the number for. My voice mail says to leave a message stating who you are if you wish to hear back from me. They call 3-5 times a day, never leaving a message.

Have received a call a day from the same prefix but different numbers, all beginning with 13**, and the one time I answered no one said a thing.

I get daily calls from this number. First couple times I answered because I live in the 360 area code and I thought it could be a legit real person/company. There was no one on the other end. Today I called back to tell them to take me off their calling list and it's some "Diversify Consulting" company or something rather.  I just hung up lol