Edtech unicorn BYJU'S is buying after-school learning app Toppr and upskilling platform Great Learning in a cash and stock deal, according to the company's regulatory filings. BYJU'S is buying Toppr in a $150 million deal and Great Learning in a $600 million deal. Valued at $16.5 billion, BYJU'S is backed by Naspers, Tiger Global Management, Chan Zuckerberg Initiative and others.