Not including Alaska:
Trump voters in Trump counties: ~38,536,000 (61%)
Trump voters in Clinton counties: ~24,285,000 (39%)
Clinton voters in Trump counties: ~20,976,000 (32%)
Clinton voters in Clinton counties: ~44,757,000 (68%)
These figures are very telling, and speak to the urban/rural divide between the two parties. Clinton's voters were heavily concentrated in populous and densely inhabited urban/suburban areas, while Trump's voters were spread out over a broad geographical area, in cities, suburbs, exurbs, and rural areas. For example, Trump received more than 453,000 votes in Cook County, which Clinton won by 54 percentage points, and 769,000 votes in Los Angeles County, where she won by 50 percentage points.
Indeed, Trump had more votes from LA County than he did in the entire state of Mississippi.
I partially wanted to know the answer to this in response to this graphic:
Such a misleading statistic. There are literally tens of millions of Trump voters living in these Clinton counties, with most of them being higher-earning and more economically-productive than the urban Democratic base of young people and minorities.