The U.S. national debt has climbed to a stunning $14.3 trillion. Who are biggest creditors of U.S., according to recent data from the U.S. Treasury?

No. 15: Russia

Estimated ownership of U.S. government debt: $151 billion. Graduates walk under stormy looking skies at sunset in Red Square near the Kremlin in Moscow. Russia has been gradually cutting back on its ownership of U.S. Treasurys since the financial crisis ended, replacing bonds as they expire with investments in gold.

No. 14: Caribbean banking centers 

Estimated ownership of U.S. government debt: $168.1 billion. A bulldozer passes on the beach of Grand CaymanIsland. The Caribbean banking centers include the Cayman Islands, the Bahamas, Bermuda, Netherlands Antilles, Panama and the British Virgin Islands.

No. 13: Taiwan

Estimated ownership of U.S. government debt: $155.1 billion. Worshipers pray at LungshanTemple, one of the city's most famous temples, in Taipei, Taiwan. The island nation has been increasing its holdings in recent months.

No. 12: Brazil

Estimated ownership of U.S. government debt: $186.1 billion. Brazil's U.S. debt holdings represent an all-time high for the South American country.

No. 11: Oil exporters

Estimated ownership of U.S. government debt: $211.9 billion. Countries that export a lot of oil naturally build up large reserves of dollars since petroleum is priced in U.S. dollars all around the world. Buying Treasurys gives them a way to recycle some of those dollars by sending them back to the U.S. in exchange for the safety of the full faith and credit of the U.S. government. This group includes: Ecuador, Venezuela, Indonesia, Bahrain, Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia, the United Arab Emirates, Algeria, Gabon, Libya, and Nigeria.

No. 10: Insurance companies

AP / Estimated ownership of U.S. government debt: $253 billion. Insurance companies need steady and predictable income that can help them plan ahead for the potential liabilities related to the insurance policies they write. They also need liquidity, or the ability to redeem assets if they need more cash to pay their policies. An active market for U.S. Treasury bonds makes them a liquid store of value that can earn interest over long periods of time and be redeemed for cash at a moment's notice, making them a perfect fit for a portion of any insurer's asset portfolio.

No. 9: United Kingdom

Estimated ownership of U.S. government debt: $271.6 billion. The U.K. is a major ally that does lot of business with

Estimated ownership of U.S. government debt: $315.7 billion. Banks often keep U.S. government debt on their books for a variety of reasons. Banks that do business with the Federal Reserve System will buy and sell Treasury bonds whenever the central banker takes action to either inject or suck money out of the U.S. economy. They are also actively used by banks as collateral in various transactions with their trading counter parties, giving them plenty of reason to keep a ready supply on their books.

No. 7: State and local governments

Estimated ownership of U.S. government debt: $519.8 billion. A young girl takes a picture of the Oregon state seal on the floor in the Capitol rotunda. Many states offer actively managed investment pools that their various government agencies as well as cities and counties can use to safely store their cash while earning a better return than they might get at a local bank. Not surprisingly, these portfolios are steered toward conservative fixed-income investments, with U.S. Treasury securities and other government bonds a common staple.

No. 6: Mutual funds

Estimated ownership of U.S. government debt: $636.4 billion. A trader works on the floor of the New York Stock Exchange. U.S. government bond funds are popular with investors seeking income and diversification but are not willing to take a lot of risk. Such funds will typically allocate a portion of their investment to U.S. Treasurys as well as bonds issued by government agencies, such as Fannie Mae.

No. 5: Pension funds

Estimated ownership of U.S. government debt: $801.7 billion. Tax-exempt investors like pension funds typically have little reason to invest in non-taxable investments, which is one reason why many stay away from municipal bonds. Treasury bonds, however, are taxable on the federal level and may offer better yields than their tax-exempt counterparts -- one major reason why many pension funds are willing to allocate at least a portion of their fixed income portfolio to Uncle Sam.

No. 4: Japan

Estimated ownership of U.S. government debt: $882.3 billion. Like China, Japan is a major U.S. trade partner with an export-driven economy. Unlike China, Japan has a free-floating currency, though its bank has from time to time intervened in the foreign currency market to weaken the yen and keep exports competitive, selling yen and buying dollars as reserves.

No. 3: China

Estimated ownership of U.S. government debt: $1.16 trillion. China's status as the world's largest export economy and the world's largest buyer of U.S. Treasury debt are closely interrelated. To make its goods more competitive on global markets, China has kept its currency artificially low by building up huge reserves of foreign currencies, including that of one of its largest trade partners, the United States. To recycle the dollars, China purchases Treasurys, which puts the money back to work and sends it back to the

No. 2: Investors (U.S. savings bonds and other)

Estimated ownership of U.S. government debt: $1.404 trillion. Individual savings bonds, such as the Treasury’s Series I Savings Bonds, are a low-risk store of value that people use to protect themselves against inflation, supplement retirement incomes, give as gifts and to save for and finance their children's education. The interest is taxable unless it is used to finance education, in which case the interest earnings can be excluded from Federal income tax.

No. 1:  The Federal Reserve and intragovernmental holdings
Estimated ownership of U.S. government debt: $5.656 trillion. The Federal Reserve's purchase and selling of Treasurys is one way the U.S. central banking regulator helps implement monetary policy. Buy buying bonds from other banks and crediting them with cash, the Fed puts more money into the U.S. banking system -- and has also built up a large store of Treasurys, having just completed a $600 billion bond buying program.