Phone interview, roughly 15 minutes. Applied through company website and received an interview a few weeks later. I was asked a series of stats/probability related questions and had to explain my approach.

Two rounds of phone interview, all of them are portability questions or math contest style questions. First one lasted about an hour, second one about 45 minutes. Questions have really elegant solutions and he will guide you towards the solution. I guess they cared about the process of how you figured out the solution rather than the solution itself.