Why should you not use Number as a constructor?

I entered this statement in JSLint:

var number = new Number(3);

And received the following message:

Do not use Number as a constructor.

Why is that? The statement is creating a number object, not a primitive value, so I don't see why using new is a problem.

EDIT: Thanks for all the responses. They've got me thinking further, so I posted a follow-up question here.