Although that rises to 40 for iPhone owners.
US smartphone owners have an average of 27 apps installed on their handsets, according to Nielsen's latest Apps Playbook research.
That's up from 22 in December last year, although the number varies by platform.
Nielsen says that iPhone owners have an average of 40 apps, compared to 25 for Android owners, and 14 for BlackBerry owners.
Its research also finds that Games continues to be the most popular app category by installations, with 61% of smartphone owners having downloaded a game in the last 30 days.
It's followed by Weather (55%), Maps/Search (50%), Social Networking (49%) and Music (42%).
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Here's the full chart, comparing smartphones to feature phones:
Nielsen also breaks down the five most popular apps for iPhone, Android and BlackBerry, with the results making happy reading for Facebook, Google Maps, Weather Channel and Pandora:
The data comes from a survey in August of more than 4,000 US mobile subscribers.
