According to comScore research, as reported by Reuters, Google+ has attracted 25 million users, making it the fastest site to achieve such a number. The firm says Google+ had 25 million uniques as of July 24, growing at about a million visitors a day.

On a side note, Groupon has been called the “fastest growing company ever,” but Google is already huge, and has hinted at future integrations between Google+ and the company’s Groupon competitor Google Offers.

comScore’s report comes after a recent report from Experian Hitwise indicating that visits and time spent on the site were on the decline in the U.S. That report came out July 27, looking at the week ending July 23. According to them, Google+ received over 1.79 million total U.S. visits that week, which was a decrease of 3% vs. the previous week. Time on site was also down 10%. None of that took into account mobile apps either. The Android app has been around since launch, and the iPhone app just launched on July 19.

Speaking of mobile apps, Google just launched an update for the Android app (which already includes a key component missing from its iPhone counterpart in Instant Uploads). Google+ Mobile Lead Product Manager Punit Soni posted the following video on Google+ discussing the update:

It comes with improved reliability of notifications (more fixes, he says, are coming in this department soon). Notifications will be grouped together.

In the stream, mentions composing mentions is faster, and when come across a mention in the app, it links to the person’s profile. You can can compose a post just to an individual from the app.

Soni says the “nearby” filter has also been improved. “This means you can see what’s happening around you,” he says.

“In addition, we have made starting huddles even easier, whether it is one one one from a person’s profile or with people in your circle, and now you can hide one on one huddles if you don’t want to see them in your list anymore,” says Soni. “But don’t worry, if you start a conversation with that person again, you will start right where you left off.”

Links now clickable in Huddles as well.