Verizon cell phone esn number?

ok, so i have an existing verizon account with a phone of mines but i broke my phone. I have this other phone that i found but i do not know if the esn number is clear. i really do not want to buy a new phone cause it will be my 3rd one in a month. how do i figure out if the esn number is clear. i do not want to give them my verizon account, i just want to know if its clear or not.