What status code should I return when part of a bulk update fails?

Let's say I'm a server responding to a request to do a bulk create of some entity. Let's say that I've also decided to make it so that if one instance of the entity can't be created, due to a server error or user error, I will still create the other entity instances. In this scenario what should I return? A 201 because I created most of the entities in the request? Or A 4xx/5xx since there was an error while creating one of the entities?