How many platforms do you use to run your business?

Before I started Opertivo, I was a virtual business operations manager for entrepreneurs and small business owners. I manage most aspects of their businesses for them - invoicing, payroll, organizing electronic files, expense management, etc. and the accompanying systems to manage said things. The most I've ever seen was a client who owned a law firm that had 11 different systems to help her manage her business. I myself had 6. I'm curious what that number is for some other founders!