We incurred interest expense to Ping An Group in the aggregate amount of RMB154.3 million, RMB67.5 million and RMB6.2 million (US$1.0 million), respectively, for the years ended December 31, 2019, 2020 and 2021, in connection with borrowings from Ping An Group and interest paid to Ping An Group for its subscription in the consolidated wealth management products managed by us, representing 0.5%, 0.2% and 0.0% of our total expenses for the years ended December 31, 2019, 2020 and 2021, respectively.
We had cash balances of RMB14.6 billion, RMB14.4 billion and RMB9.6 billion (US$1.5 billion) held at banks who are affiliates with Ping An Group as of December 31, 2019, 2020 and 2021, respectively, representing 9.8%, 5.8% and 2.7% of our total assets as of December 31, 2019, 2020 and 2021, respectively.
We had account and other receivables and contract assets due from Ping An Group in the amount of RMB2,784.8 million, RMB2,040.9 million and RMB3,052.1 million (US$478.9 million) as of December 31, 2019, 2020 and 2021, respectively, representing 1.9%, 0.8% and 0.8% of our total assets as of December 31, 2019, 2020 and 2021, respectively.
As of December 31, 2019, 2020 and 2021, we had balance of financial assets at amortized cost and financial investments (loans and receivables) and financial assets at fair value through profit or loss with Ping An Group in the amount of RMB6,903.3 million, RMB7,189.1 million and RMB4,779.9 million (US$750.1 million), respectively, primarily in connection with certain asset management plan products we purchased from Ping An Group, representing 4.6%, 2.9% and 1.3% of our total assets as of December 31, 2019, 2020 and 2021, respectively.
As of December 31, 2019, 2020 and 2021, in addition to the convertible promissory notes we issued to China Ping An Insurance Overseas (Holdings) Limited as described below, we had no borrowings due to Ping An Group.
As of December 31, 2019, 2020 and 2021, we had account and other payables and contract liabilities due to Ping An Group in the amount of RMB2,521.4 million, RMB1,888.1 million and RMB801.7 million (US$125.8 million), respectively, representing 2.5%, 1.1% and 0.3% of our total liabilities as of December 31, 2019, 2020 and 2021, respectively.
Convertible Promissory Notes Issued to China Ping An Insurance Overseas (Holdings) Limited and An Ke Technology Company Limited
In October 2015, in connection with our acquisition of the retail credit facilitation business from Ping An Group, we issued convertible promissory notes in an aggregate principal amount of US$1,953,800,000 to China Ping An Insurance Overseas (Holdings) Limited. The acquisition was consummated in May 2016. On the same date, China Ping An Insurance Overseas (Holdings) Limited agreed to transfer US$937,824,000 of the outstanding principal amount of the notes and all rights, benefits and interests attached thereunder to An Ke Technology Company Limited.
Each of the notes bears interest from the date of issuance, unless otherwise agreed, at the rate of 0.7375% per annum of the principal amount of each of the notes outstanding from time to time, which will be payable by us semi-annually until the eighth anniversary of the issuance date of the notes. Subject to the terms and conditions set forth in each of the notes, each of China Ping An Insurance Overseas (Holdings) Limited and An Ke Technology Company Limited has the right in the manner provided in the notes, as applicable, to convert the whole or any part of the outstanding principal amount of the notes, as applicable, into our ordinary shares, par value US$0.00001 per share (or the American depositary shares representing our ordinary shares), during the period commencing on April 30, 2023 to the date which is five business days before the maturity date (exclusive) at an initial conversion price of US$14.8869 per ordinary share subject to certain adjustments as set forth in each of the notes. Unless previously converted or purchased and canceled, we shall redeem each of the notes at 100% of its principal amount together with accrued interest on the maturity date.
For the years ended December 31, 2019, 2020 and 2021, the contractual interest we were required to pay on the convertible promissory notes were US$7.5 million, US$7.5 million and US$7.5 million to China Ping An Insurance Overseas (Holdings) Limited and US$6.9 million, US$6.9 million and US$6.9 million to An Ke Technology Company Limited, respectively.