We're dividing 387621 by 21 
We want to figure out the number of times 387621 can be divided by 21.

Moving on to step 1:
If we divide 3 by 21, we get 0 and a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Bring next digit (8) of the dividend behind the 3 and repeat the process: 38 / 21

Let's proceed to step 2:
If we divide 38 by 21, we get 1 and a remainder of 17.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we subtract 21 from 38, we get 17.
Include the next digit (7) from the dividend after 17, then repeat: 177 / 21

Let's proceed to step 3:
21 goes into 177 8 times with a remainder of 9.
Put 8 as the next digit of the answer. 
Result so far: 18.0
If we take 168 away from 177, we end up with 9.
Bring next digit (6) of the dividend behind the 9 and repeat the process: 96 / 21

Step 4:
21 can be fit into 96 4 times, resulting in a remainder of 12.
Record the quotient 4 as the next digit in the result. 
Result so far: 184.0
Subtract 84 from 96 to get 12.
Fetch the next digit (2) from the dividend, attach it to 12 and continue: 122 / 21

Advancing to step 5:
If we divide 122 by 21, we get 5 and a remainder of 17.
Write down 5 as next digit of the result. 
Result so far: 1845.0
The remainder is 17 after subtracting 105 from 122.
Fetch the next digit (1) from the dividend, attach it to 17 and continue: 171 / 21

Moving on to step 6:
If we divide 171 by 21, we get 8 and a remainder of 3.
Record the quotient 8 as the next digit in the result. 
Result so far: 18458.0
Deduct 168 from 171 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.

On to step 7:
21 can be fit into 30 1 times, resulting in a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 18458.1
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.

Moving on to step 8:
The number 21 fits into 90 4 times, leaving a remainder of 6.
The next digit of our result is 4. 
Result so far: 18458.14
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.

Going ahead to step 9:
21 goes into 60 2 times with a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 18458.142
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.

Advancing 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: 18458.1428
Deduct 168 from 180 and we're left 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.

On to step 11:
21 goes into 120 5 times with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 18458.14285
The remainder is 15 after subtracting 105 from 120.
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 12:
21 can be fit into 150 7 times, resulting in a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 18458.142857
Subtracting 147 from 150 leaves us 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.

Moving on to step 13:
If we divide 30 by 21, we get 1 and a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 18458.1428571
Subtracting 21 from 30 leaves us 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.

Moving on to step 14:
If we divide 90 by 21, we get 4 and a remainder of 6.
The next digit of our result is 4. 
Result so far: 18458.14285714
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

In conclusion, the division gives 18458.14285714 with a balance of 6e-09.