The four Big Tech CEOs who will testify before Congress Wednesday command global empires with power and wealth that make them more like countries than companies.

By the numbers: Here are four very large stats for Facebook, Apple, Google/Alphabet and Amazon that tell the story of their value, scale and influence.

$5 trillion: The four companies' (rough) combined market capitalization.

• That number changes by the day, of course. Apple, with its premium consumer devices, and Google and Facebook, who depend on ad revenue, could be vulnerable to a long-lasting pandemic-driven downturn.
• But for the time being, they constitute four of the top five most valuable American companies to trade on public markets. (The other one, which is also often considered a member of the Big Tech club, is Microsoft.)
• Five years ago, the other six companies in the top 10 were worth about 90% of the combined market cap of the big four. Now, they're worth about 75% as much. Even as the market and its most valuable firms have risen dramatically in value, the big four have risen more.

$773 billion: the four companies' combined annual revenue at last count.

Broken out by company, they made the following in fiscal 2019 (also calendar 2019 for all but Apple, whose fiscal year starts with the fourth calendar quarter):

• Facebook: $70.7 billion, in the same ballpark as Venezuela's gross domestic product.
• Alphabet: $161.9 billion, a bit north of Ukraine's GDP.
• Apple: $260.2 billion, close to Vietnam's GDP.
• Amazon: $280.5 billion, around Pakistan's GDP.

Together, revenue for all four add up to roughly the GDP of Saudi Arabia.

$420 billion: the combined total cash pile of the four firms (per data from FactSet, when they last reported earnings).

That breaks down to about:

• $49.6 billion for Amazon
• $60.3 billion for Facebook
• $117.2 billion for Alphabet
• $192.8 billion for Apple

Those fat cash hoards give them flexibility to make ambitious internal investments, freedom to buy up potential competitors, the option to juice shareholder value through stock buybacks, and cushioning to weather crises.

4.6 billion: Human beings on earth who are connected to the internet (according to one recent estimate).

These companies all aim to connect anyone who can get online to goods, services and other people. Their scale is limited only by how many people they can reach.

• The world isn't all open to them, of course. Facebook and Google aren't in China, home to the largest population of internet users in the world. Amazon only operates its core e-commerce platform in certain countries (and has stumbled in efforts to crack into some key markets, including China). And Apple's high-end devices are out of reach for billions of people.

Despite those limits, these companies are operating at a scale that no previous industry has achieved.

• Google crossed the 2 billion user mark for its G Suite of products (which includes Gmail along with productivity apps like Google Docs) earlier this year. The company's YouTube notched 2 billion monthly active users last year.
• Facebook had 2.6 billion monthly active users as of Q1 this year.
• By the end of last year, Apple had 1.5 billion devices in active use by people around the world.
• Amazon doesn't publicly state how many people have accounts, but CEO Jeff Bezos did reveal in 2018 that the company had passed 100 million Prime customers in the U.S.

Our thought bubble: The big four companies shape people's lives — what goods they can obtain, what media they're exposed to, how they connect with friends and family, how they understand the world. That's a stunning amount of power to entrust to a handful of companies run by a handful of men.