It is one of the world's largest hedge funds, with $121bn under management, but its name is virtually unknown in financial circles. Braeburn Capital is not operated from the top floor of a Manhattan skyscraper or a plush Mayfair townhouse. It is located in a quiet suburb of Nevada's capital, Reno, and it belongs to Apple.

In a nondescript building opposite an abandoned restaurant, a small number of advisers have been charged with investing the cash pile Apple has amassed thanks to the seemingly insatiable global appetite for its consumer electronics.

That pile has grown from $9bn when Braeburn was established in 2006 to more than $120bn (£75bn), according to Apple's financial results on Thursday. That is a shade less than the $130bn Bridgewater Associates, the largest hedge fund in America and probably the world, has under management.

Much of Apple's money is trapped overseas, sheltered from the US taxman, who would demand a 35% cut were the money to be repatriated. But it can be invested at home. Apple's financial reports show it holds $21bn of US government debt – a vast sum for a single private investor. Foreign governments like investing in US securities, but Apple owns more than the $19bn held by Malaysia, and just $4bn less than Spain.

Apple's largest investment category is corporate securities. It has $44.5bn in company shares, more than the entire $39bn managed by Man Group, the UK's largest hedge fund. It is also a big holder of other nations' debt, with $7bn invested in sovereign securities abroad.

Little is known about which companies Apple invests in. It occasionally owns stakes large enough to be declared: Apple was a founding investor in British chip designer ARM, but has sold out, and owns 9% of Hertfordshire-based Imagination Technologies, which designs video and audio chips.

Braeburn does not file a record with the American stock market regulator, or the Investment Adviser Public Disclosure register; it is not an independent adviser but a division of a private company.

It is free to hold any assets – for all anyone knows they could be short positions on the shares of its major rivals such as Samsung and Google, or the sub-prime mortgages of American homeowners, lumped together and traded on the financial markets. Indeed, it declares ownership of nearly $9bn of mortgage and asset-backed securities, according to filings.

The decision to locate Braeburn in Nevada rather than Apple's home state of California makes sense because Nevada does not collect corporation tax or capital gains tax. California, by contrast, has a corporate tax rate of 8.84%, a rate of contribution to the public coffers that has not been enough to prevent a school funding crisis in a state that houses some of the world's most valuable companies. Managing its money from Nevada also allows Apple to lower its tax bills in other states. Florida, New Jersey and New Mexico discount taxes when a company's financial management is in another jurisdiction.

In 2006, Apple listed only cash and short term investments in its filings, but Braeburn's managers are expected to take the long view. Apple now holds nearly $90bn of its money in "long-term marketable securities".

According to analysis by the New York Times, since founding Braeburn, Apple has earned more than $2.5bn in interest and dividend income on its cash reserves and investments around the globe.

Apple declined to comment on Braeburn's activities, but in the year its investment arm was established, an Apple spokesman explained that it would function as a regional treasury office, on a par with existing offices at its Cupertino headquarters, in Singapore and in Cork, Ireland.

The Nevada Annual Report, a register of companies located in the state, lists three Braeburn officers: Apple attorney Gene Levoff, Michael Shapiro and Gary Wipfler, who as Apple's treasurer is the person officially responsible for the management of the technology titan's billions.

Various Braeburn employees have filled in pared down profiles on LinkedIn, the corporate networking site, including Steve Johnson, who claims to be chief investment officer, and Rhys Gray, a chartered financial accountant previously employed by investment management firm Payden & Rygel.

Ted Mulvaney describes himself as a portfolio manager at Braeburn, and is also linked to Magrathea Financial Services, a Reno based investment firm named after a Hitch-Hiker's guide to the Galaxy planet, known as one of the wealthiest in the universe due to its extraordinary trade – building customised planets to order.

Braeburn's team may be modest, but its scope is galactic.