Number of Apple employees in the US: 43,000.
Number of Apple employees in the mother-of-all-factories in China: 430,000.
Number of employees at GM at its peak: I could swear I saw the number 430,000 again (which is, obviously what set me out to write this post). But Google is unavailing. Here's an older NYT clip that says GM US had "more than 600,000 workers in 1979."
Oh and: UAW membership in 2010: 430,000, down from a peak of 1.5 million.