Amazon gave away a tiny inkling of how big its Amazon Prime program has grown: it likely has at least 20 million members, with one million of those members signing up in the third week of December during the run-up to Christmas, according to a press release from the company. In fact, the press release indicates that the take-up rate was so brisk that the company had to at times limit new sign-ups "to ensure service to current members was not impacted by the surge in new membership."

The company hit its peak sale rate on Cyber Monday, when customers were ordering 426 items per second. Amazon stated that “millions” of customers bought Kindle e-readers and Kindle Fire tablets, though it didn't break out specific numbers for either type of device.

Analyst estimates previously pegged Amazon Prime’s base as somewhere between 16 and 18 million members, per the New York Times. Amazon generally charges $79 a year for Prime membership, though there are discounted versions of the service for students and “moms.” In the press release, Amazon refers to its Prime subscriber base as being made up of "tens of millions of members" scattered around the world.

Prime offers unlimited two-day shipping for free to its members, though some items must be part of a $25-or-more package. Amazon announced in November that it was entering a partnership with the US Postal Service to offer delivery seven days a week. Following the announcement of that feature, along with the encroaching holiday and the drone stunt, Amazon appears to have turned a large number of casual online shoppers into newly minted Prime customers.