Citigroup (C) is stockpiling money the way my son hoards his precious stash of post-Halloween candy. No one is allowed to touch it.

As a result, Citigroup has nearly doubled its cash to a monstrous $244.2 billion in the last year, Bloomberg reports. It's the biggest cash heap of any U.S. bank, and it has people scratching their heads.

Two questions to ask on this piece of news. Why is Citigroup holding on to all that money? And why on Earth hasn't the bank repaid its taxpayer bailout?

Citigroup isn't the only bank doing this. The four largest U.S. banks, which include Bank of America (BAC), Citigroup, Wells Fargo (WFC) and JPMorgan (JPM) have increased their combined liquidity by 67% from June of 2008.

"When you go through a near-death experience, it focuses the mind, and none of these people want to ever go through it again," a banking analyst told Bloomberg.

All of which is infuriating to government officials, who are trying to get the banks to start lending money to people and small businesses again.

Try getting a mortgage from one of these banks if you don't have perfect credit or 20% down. Ha. That's why so many people are flooding the government's Federal Housing Authority with loan applications.

Basically, these banks are acting like the recession isn't over and another major financial crisis is on the way. They're holding on to the cash for a worst-case scenario of waves of customers rushing in to pull their money.

“In my 44 years in the business, I have never seen a company with remotely as much cash as this,” well-known banking analyst Richard Bove said of Citigroup's hoard, Bloomberg reported.

The irony here is that Citigroup could be making so much more money if it would lend it out. The bank could get nearly $9 billion more in annual interest revenue if it put its cash into loans, according to Bloomberg.

But Citigroup doesn't want to risk some of those loans defaulting.

Bove said that even though it makes no sense for Citigroup to have that much cash, the bank doesn't have much choice. "You either keep that cash or you’re dead," he told Bloomberg.

So will Citigroup repay the government the $20 billion it still owes in bailout money? Not anytime soon, analysts say.

But at least the Treasury seems to be making a profit here. The Treasury has already converted $25 billion of Citigroup's bailout debt into common shares, and the share price has quadrupled from the record low of $1.02 hit after the conversion, Bloomberg reports.

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