Amazon now employs a whopping 542,000 people and plans to hire thousands more

Ted S. Warren/AP

• Amazon's employee base swelled an astounding 77% from the end of June to the end of September.
• The retail giant now employs 541,900 people, up from 382,400 last quarter and 306,800 a year ago.
• It is one of only two companies in the nation to employ over half a million people.

It's hard to imagine a company that already employed 382,400 people could grow its headcount 77% in just three months.

But that's exactly what Amazon did. At the end of September, the e-commerce giant employed 541,900 people, up 159,500 from the end of June.

The boost in employees mostly came from Whole Foods, which Amazon acquired in August. That deal added 90,000 people to Amazon's payroll. But even setting that deal aside, Amazon still brought on board 70,000 additional new employees.

An undisclosed number of those came from Souq.com, the Middle East's biggest e-commerce player, which Amazon also bought last quarter, Brian Olsavsky, Amazon's chief financial officer, told analysts during the company's quarterly conference call on Thursday. Excluding Whole Foods and Souq, Amazon's headcount would have grown 47%, Olsavsky said.

Amazon is now the second largest US company by headcount. However, it's still a long way behind Walmart, which has 2.3 million employees.

But Amazon isn't done growing or hiring. The company said it plans to hire 120,000 seasonal workers for its warehouses and customer services centers this holiday season. After last year's holiday season, Amazon ended up hiring many of its seasonal workers full time, and it plans to do the same thing again this year, the company said. Meanwhile, the company has grown its warehouse space by 30% this year, Olsavsky said.

The company is hiring an army of office workers as well. It has 14,000 job openings listed on its website, over 7,000 of which are for software engineers. Another 2,500 of the openings are for sales people, mostly focused on promoting its Amazon Web Services cloud computing service to businesses.