All function instances have a [[Call]] property. In most cases a different [[Get]] method.
Functions returned by bind have a special [[HasInstance]], [[Scope]], [[Construct]], [[FormalParameters]], [[Code]], [[TargetFunction]], [[BoundThis]] and [[BoundArgs]] property (see 8.6.2, 13.2, 15 and 15.3.4.5).
The [[Class]] property is "Function".
Functions in strict mode or created by bind (15.3.4.5) have two properties named "caller" and "arguments" which throw a TypeError when you try to get or set them.