How many hearts Does the Arctic whale have?

There are many types of whales in the world.

But some whales have special circulation system:they have 4 hearts

It's because to ensure that the brain and heart muscle have the best oxygen supply to conserve oxygen during a long dive. And another reason is because

the it has enormous body and hearts needs to be very strong that it can supply oxygen to the whole body.

P.S: Their hearts can be upto the size of a minivan to the size of a double decker bus.