One of the least celebrated but most charming of standard movie plot propellers is the Impregnable College, that most intimidating and rigid of institutions––––usually Harvard or Yale something-or-other, law, medical, you name it. The school represents both the great dream of the protagonist and his or her insurmountable challenge––––to get in, to fit in, to raise enough money to go, etc.

The funny part is that the institutions that Hollywood sets up at the arrival end of the American Dream are invariably portrayed as cold, towering, and unhelpful. In reality, many of the nation’s top schools have stellar financial aid programs and a stated interest in helping disadvantaged or unusual candidates get accepted and thrive as students.

The Hollywood Harvard, however, is always an unyielding ivory tower, and it appears this week in “21,” where young Ben Campbell is a moppy working-class Boston kid who needs $300,000 for Harvard med school. Never mind that he’s the smartest kid at MIT and could probably get some fantastic scholarships even without the full-ride package the movie dangles in front of him in its opening scene. That wouldn’t be momentum enough for this popcorn story. The fact of the matter is Ben needs $300,000, and an opportunity to get it comes to him when he catches the eye of snarky MIT professor Micky Rosa (Kevin Spacey, so underchallenged he may as well have done the role drunk).

See, Ben is such a math whiz that Micky and his crew of slinky students figure Ben might be pretty good at counting cards in Blackjack. If you don’t know what counting cards means, I don’t either and I sat through this 2-hour movie while it tried it to explain it again, and again, and again. It’s not that counting cards is that complicated––––the movie just has other things on its mind.

Like a relentless, oversexed barrage of flashy montages, amped-up club beats and swirling views of Vegas hotspots. Ben and Micky and their team take to hitting the Strip every weekend to make easy money, and director Robert Luketic wastes no time wringing out every clichéd Vegas visual into the bucket of over-funded, ultra-FX pop, until, darn it all, I found myself buying into the gang’s impossibly sexy high-roller lifestyle and wanting to go along myself.

Now, why Ben would ever accept the ludicrous offer to join Micky’s team (oh, but he needs that $300,000!) is never really believable, nor is the moment when he succumbs to his greed and shoots to keep gambling even after he’s raked in more than the 300K––––but after a point the movie’s pep overwhelms even its inability to make us care about the characters, and we glide along for the ride.

The story is a rags and riches rollercoaster, of course, as Ben starts to lose control at the tables and alienate his dorky, loveable friends back in Massachussetts, before bouncing back in a series of improbable closing twists.

“21,” believe it or not, is based on the true story of a group of Vegas-busting MIT students recounted in the 2003 book “Bringing Down the House,” but there’s little trace of the realism and gravity of a true story here.

“21” might have been an enthralling case study in the obsession and addiction of gambling. But it’s not. It’s a blandly satisfying caper romp, good enough for a tub of popcorn but hardly worth the amount of reflection and thought it has taken to write this review. If you’ve played enough Blackjack and have nine bucks to throw around, that may be all you need.