A million here, a million there. Pretty soon you're talking real figures.

The "Storm Area 51" event that went viral last month as people pledged to crash the secret military base in an attempt to "see them aliens" has only grown in scale in recent weeks. More than 2 million Facebook users have now said they are going, up from slightly more than 400,000 two weeks ago and 1.5 million people as of July 17.

An additional 1.4 million people have said they are interested in attending the event.

AREA 51 EXPERT ON SOCIAL MEDIA CAMPAIGN TO 'STORM' TOP-SECRET SITE: MILITARY WON'T LET ANYONE GET CLOSE

Following the craze, British oddsmaker BookMaker.eu placed odds on the number of sign-ups for the event, with the over/under set at 2.3 million. The odds on the over were most recently at -160 and the under was at +130. That means a better who bet $100 would win back their original bet plus $130 if less than 2.3 million people attend.

BookMaker.eu also put odds on the number of arrests and whether aliens will actually be discovered. With regard to the number of arrests, based on what USA Today reports at the time of the event, the over/under is set at 9.5, with the under attracting most of the money, offering -350 odds.

As to whether aliens are actually discovered, the odds are in overwhelmingly in favor of No, at -40,000. That means a person would have to bet $40 just to win $1. But if for some reason the people manage to get through and E.T. is found running around, bettors will be rewarded handsomely, with the odds on Yes at +4,000.

While the event, which takes place Friday, Sept. 20 between 3 AM and 6 AM PDT, has garnered significant media attention, it's highly unlikely anything will come of it.

U.S. Air Force spokeswoman Laura McAndrews recently issued a statement saying the Air Force "would discourage anyone from trying to come into the area where we train American armed forces," adding that it [the U.S. Air Force] "always stands ready to protect America and its assets."

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Annie Jacobsen – author of "Area 51: An Uncensored History of America's Top Secret Military Base – recently told Fox & Friends that she dismissed the idea that civilians could get close to the facility. She explained that the classified military facility is housed inside a classified testing and training range which is the size of Connecticut.

"That base is so jealously guarded, both in terms of media and in terms of actual physicality," said Jacobsen. "I don't think the Air Force or any of the other military partners or intelligence community partners that are all working out there at Area 51 are gonna let anybody anywhere near the entrance to Area 51."

It has, however, spawned sibling events, including the "Storm the Bermuda Triangle" event, which was set up by Dominick Carnovale, who said attending the Area 51 event would be "dangerous."

"I honestly just don't want people to attend the Area 51 event because I don't want people getting shot or arrested," Carnovale told Fox 5 NY.

A "Storm Loch Ness" event to look for the Loch Ness Monster has been created as well.

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Fox News' David Montanaro and Paulina Dedaj contributed to this story.