Pretty soon, Apple will reach yet another milestone with its ubiquitous smartphone. Despite the relatively underwhelming current sales of the iPhone SE and the equally subdued sales of the iPhone 6S, the company is nonetheless approaching the one billion mark - that's one billion iPhones sold since Steve Jobs unveiled the first smartphone back in 2007.

When the first iPhone was introduced nine years ago, many were skeptical that a device resembling a glass slab would be able to provide ample competition to the smartphone giants of the day. With its intuitive UI and design, however, the iPhone eventually proved itself, becoming Apple's best-selling product over the years.

In fact, the iPhone's popularity became so great, much of Apple's revenue comes from the sales of its flagship handsets. Considering the trends of iPhone sales, such results are quite unsurprising. After all, between July 2007, when the device first went on sale, up until the end of 2015, Apple has managed to sell 896 million iPhones.

Analysts believe that considering the trends in iPhone sales, even taking into consideration the relatively lackluster sales of the mid-range iPhone SE and the not-so-stellar demand for its flagship, the iPhone 6S and 6S Plus, the tech giant would probably still sell about 946 million iPhones by the end of the year's first quarter.

In the current quarter, analysts believe that Apple will probably be able to sell another 44 million iPhone units worldwide, pushed by the demand for Apple products in countries such as China. If analysts are correct, Apple will be entering the second half of the year with a total of 990 million iPhones sold.

Of course, with the upcoming release of the highly-anticipated iPhone 7, 7 Plus and possibly even the iPhone 7 Pro, the number of total iPhones sold would probably get even bigger. After all, this year signifies a full iPhone upgrade cycle for Apple. Thus, the sales of the upcoming units are expected to be very satisfactory.

Apple crossed the one billion mark when the company sold its one billionth iOS gadget in November 2014. Of course, such a number then pertained to all iOS devices, including Apple's iPod and iPad line.

This upcoming milestone, which only involves the statistics of a single device, stands as an even bigger milestone for the tech giant.

If the year's iPhones sell very well, and if Apple could repeat the feat on next year's launch, Apple might very well be on its way towards selling its two billionth iPhone by 2020.