Automated Video interview, asking about motivations. There may well have been some numerical tests but I don't remember taking them. This was followed by two face-to-face interview rounds, each consisting of 2 interviews with two interviewers per interview (a total of four face-to-face interviews).

Recruiter was very helpful and assisted me with finding the appropriate internship position. BlackRock interviews are normally impersonal and to get through it you really need to know your stuff. Know everything on your resume, and definitely prepare all the interview questions you can find online. Research BlackRock to understand what their company culture and philosophy is all about. Also, I thought I had no chance of getting it based on how the person reacted but apparently end shouldn't read too much into that.