Google’s Nexus 4 has undoubtedly been one of the hottest Android handsets on sale this holiday season, and it’s been selling rapidly since its release back in November. The search giant has even had to apologize for the difficulties LG is facing in keeping up with the impressive demand. Exactly how many Nexus 4 handsets have been sold, however, is somewhat a mystery.

Google never announces its device sales, and LG’s been keeping quiet when it comes to the Nexus 4, too. However, some Android enthusiasts have been keeping track of Nexus 4 serial numbers, and they estimate that around 400,000 units were produced by the end of 2012.

According to TechCrunch, the group of XDA Developers members arrived at the figure by taking IMEI numbers of their devices and backtracking the production numbers using an LG mobile link that’s usually used for finding new firmware. When the IMEI number is entered into LG’s system, it spits out a long string of characters that look something like this: “LGE960 ACAGBK 212KPHG188745 20121206 GLOBAL/GLOBAL N N.”

That long string of characters can then be used to determine things like the handset’s model number, its color, its storage size, and more interestingly, the country in which it was sold, its production month, its production country, and the line or production number. It’s that last one that helps establish how many handsets have been built to date.

The enthusiasts put together a long list of Nexus 4 production numbers and found that LG made around 70,000 units in October, 90,000 in November, and 210,000 in December. Given that the Nexus 4 has been selling faster than LG can make them, it’s safe to say almost all of these units have now been sold.

What’s interesting about these number is that it suggests Google and LG have been very conservative with the Nexus 4 launch. It’s almost as if they didn’t expect it to be anywhere near as big as it was.

• SourceXDA Developers
• ViaTechCrunch