To divide 3.6721 by 4, we can use long division. The first step is to place the dividend, 3.6721, under the division symbol, and the divisor, 4, outside the division symbol. We then ask, how many times does 4 go into 3? Since 4 is greater than 3, we cannot divide 3 by 4, so we bring down the next digit, 6, and ask how many times 4 goes into 36. The answer is 9, so we write 9 above the 6, and subtract 36 - 36 to get 0. We then bring down the next digit, 7, and ask how many times 4 goes into 0. Since 4 is greater than 0, we cannot divide 0 by 4, so we add a decimal point and a 0, and ask how many times 4 goes into 7. The answer is 1 with a remainder of 3, so we write 1 above the 7 and bring down the next digit, 2. We add a decimal point to the quotient and ask how many times 4 goes into 32. The answer is 8, so we write 8 above the 2, and subtract 32 - 32 to get 0. We then bring down the next digit, 1, and ask how many times 4 goes into 1. Since 4 is greater than 1, we cannot divide 1 by 4, so we add a decimal point and a 0, and ask how many times 4 goes into 10. The answer is 2 with a remainder of 2, so we write 2 above the 1, and bring down the final digit, 0. We add a decimal point to the quotient and ask how many times 4 goes into 20. The answer is 5, so we write 5 above the 0, and subtract 20 - 20 to get 0. Therefore, the final answer is 0.9180.
So, 3.6721 divided by 4 is 0.9180.