Found 3 exchanges where USDC is traded for BTC. According to the data on 24 August the most optimal price to exchange USDC for BTC is ₿0.000013 for 1 USDC. This rate is fixed at ChangeNOW at the maximum trading volume of the pair USDC/BTC - 12.8 BTC.
The maximum daily trading volume is observed in the USDC/USDT trading pair at Tapbit and reaches ₿ 5 089.16 (17.16% of the exchange's total trading volumes) at the price ₿ 0.000013 per 1 USDC.
The minimum price to buy USDC for BTC is 0.000012 - on the exchange Bithumb.
The maximum price to buy USDC/BTC is 0.000012 - on the exchange Upbit.
Warning: some USDC markets show an abnormally wide spread — those quotes may be unreliable (thin liquidity or off-market trades). Cross-check the volume against several venues.