What bank do most millionaires use?

I'm curious, could you tell me which bank is most commonly utilized by individuals who have reached the millionaire status? It's fascinating to think about the financial institutions that cater to the wealthy and the services they offer to maintain and grow their clients' wealth. Are there any particular banks that stand out in terms of their clientele base among millionaires, or is it more diverse, with millionaires opting for a variety of banking options based on personal preferences and needs?