First Google search https://www.malwarebytes.com/blog/news/2025/08/77-malicious-...
Here's 77 found by researchers and then removed. Relying on researchers to find malware isn't a very good bet.
If I were a betting man, I would say there are thousands of apps on the play store that you can classify as malware.
We will never know the true number because one of the primary goals of malware is to be as difficult to detect as possible. They're not going to declare they're malware, duh.
If you know of some algorithm to detect malware, I'd love to hear it. Evidently even trillion dollar companies cannot come up with one. To this day, the best way to detect malware is source code analysis and thorough behavior testing.
Google and Apple do neither. Those are just the facts. Do with that what you will, I don't care.