Amazon disclosed Friday that it owns a 20% stake in Rivian, the electric automaker that filed for an IPO earlier this month. As of September 30, the e-commerce giant held equity investments, including preferred stock of Rivian that represented about 20% ownership interest, according to the filing. That holding had a “carrying value” of $3.8 billion, up from $2.7 billion as of December 31, 2020. The disclosure, which popped up in a regulatory filing , provides fresh insight into how closely Rivian’s future is tied to Amazon. Amazon has invested $1.345 billion into Rivian, according to the EV maker’s initial public offering. Amazon also recently purchased $490 million worth of convertible notes in Rivian that will convert to Class A shares after the IPO, pursuant to certain pricing provisions. Amazon is not only an investor in Rivian; it’s also a customer. In September 2019, Rivian entered into an agreement with Amazon to produce 100,000 electric delivery vans. Rivian disclosed earl...