I saw somewhere that someone was running a Full node on a Lenovo T440 Thinkpad with an Intel i5, 4GB of RAM and a 500GB HDD. 
With the blockchain size reaching 140 GB, that guy is soon going to run out of space.
Unless you are not going to use your laptop for anything else, I think 4 GB of RAM will not be sufficient. It is best to get one with at least 6-8 GB of RAM.