166386 divided by 21 
Our goal is to divide 166386 by 21.

Going ahead to step 1:
When dividing 1 by 21, we get 0 with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Fetch the next digit (6) from the dividend, attach it to 1 and continue: 16 / 21

Let's proceed to step 2:
21 goes into 16 0 times with a remainder of 16.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 16 leaves us with 16.
Fetch the next digit (6) from the dividend, attach it to 16 and continue: 166 / 21

Moving on to step 3:
When dividing 166 by 21, we get 7 with a remainder of 19.
The next digit of our result is 7. 
Result so far: 7.0
Deduct 147 from 166 and we're left with 19.
Bring next digit (3) of the dividend behind the 19 and repeat the process: 193 / 21

Moving on to step 4:
The number 21 fits into 193 9 times, leaving a remainder of 4.
Put 9 as the next digit of the answer. 
Result so far: 79.0
Subtracting 189 from 193 leaves us with 4.
Append the next digit (8) from the dividend to 4 and continue with: 48 / 21

Let's proceed to step 5:
If we divide 48 by 21, we get 2 and a remainder of 6.
The number 2 becomes the next digit in our result. 
Result so far: 792.0
The remainder is 6 after subtracting 42 from 48.
Grab the next digit (6) from the dividend, add it to 6, then carry on: 66 / 21

Advancing to step 6:
When dividing 66 by 21, we get 3 with a remainder of 3.
The next digit of our result is 3. 
Result so far: 7923.0
Subtract 63 from 66 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 7:
21 can be fit into 30 1 times, resulting in a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 7923.1
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

On to step 8:
The number 21 fits into 90 4 times, leaving a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 7923.14
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.

Moving on to step 9:
60 divided by 21 is 2 with a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 7923.142
Subtracting 42 from 60 leaves us 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 10:
21 goes into 180 8 times with a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 7923.1428
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 11:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 7923.14285
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.

On to step 12:
If we divide 150 by 21, we get 7 and a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 7923.142857
Deduct 147 from 150 and we're left with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Going ahead to step 13:
If we divide 30 by 21, we get 1 and a remainder of 9.
The next digit of our result is 1. 
Result so far: 7923.1428571
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Advancing to step 14:
When dividing 90 by 21, we get 4 with a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 7923.14285714
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.

Our division results in 7923.14285714 with a remaining 6e-09.