What does the abbreviation “mm” mean in relation to digital circulation?

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Question by Cris: What does the abbreviation “mm” mean in relation to digital circulation?
In reviewing the Media Kit for Entertainment Weekly (magazine) they reference what their digital circulation is as well for EW.com. However, they use an abbreviation that I am unfamiliar with in terms of measuring circulation. For example, they say:

EW.com
Avg. 6.9mm uniques YTD 2010
Avg 86mm PageviewsYTD 2010

EW.com Mobile Site Record September
4.2mm Pageviews; +60% MOM
1.1mm Uniques; +138% MOM
Average time spent: 5.5 minutes/visit

Social Media
1.5mm @EW Twitter followers
30,000 Facebook fans
3.4MM Social media referrals

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