388866 divided by 21 
Our goal is to divide 388866 by 21.

Advancing to step 1:
21 can be fit into 3 0 times, resulting in a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Append the next digit (8) from the dividend to 3 and continue with: 38 / 21

On to step 2:
When dividing 38 by 21, we get 1 with a remainder of 17.
Write down 1 as next digit of the result. 
Result so far: 1.0
Deduct 21 from 38 and we're left with 17.
Grab the next digit (8) from the dividend, add it to 17, then carry on: 178 / 21

On to step 3:
21 goes into 178 8 times with a remainder of 10.
Write down 8 as next digit of the result. 
Result so far: 18.0
Deduct 168 from 178 and we're left with 10.
Grab the next digit (8) from the dividend, add it to 10, then carry on: 108 / 21

On to step 4:
If we divide 108 by 21, we get 5 and a remainder of 3.
Use 5 as the next digit of our solution. 
Result so far: 185.0
If we take 105 away from 108, we end up with 3.
Grab the next digit (6) from the dividend, add it to 3, then carry on: 36 / 21

Advancing to step 5:
36 divided by 21 is 1 with a remainder of 15.
Use 1 as the next digit of our solution. 
Result so far: 1851.0
If we subtract 21 from 36, we get 15.
Take the next digit (6) from the dividend and append it to 15, then repeat: 156 / 21

Going ahead to step 6:
The number 21 fits into 156 7 times, leaving a remainder of 9.
Use 7 as the next digit of our solution. 
Result so far: 18517.0
If we take 147 away from 156, we end up with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Going ahead to step 7:
21 goes into 90 4 times with a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 18517.4
Deduct 84 from 90 and we're left with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 8:
When dividing 60 by 21, we get 2 with a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 18517.42
Deduct 42 from 60 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Moving on to step 9:
If we divide 180 by 21, we get 8 and a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 18517.428
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 10:
When dividing 120 by 21, we get 5 with a remainder of 15.
The next digit of our result is 5. 
Result so far: 18517.4285
Subtracting 105 from 120 leaves us with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 11:
150 divided by 21 is 7 with a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 18517.42857
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 12:
If we divide 30 by 21, we get 1 and a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 18517.428571
If we subtract 21 from 30, we get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 13:
21 can be fit into 90 4 times, resulting in a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 18517.4285714
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 14:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 18517.42857142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Our division results in 18517.42857142 with a remaining 1.8e-08.