We look at the division of 813587 by 21 
We're looking to find how many times 21 goes into 813587.

Moving on to step 1:
If we divide 8 by 21, we get 0 and a remainder of 8.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 8 after subtracting 0 from 8.
Take the next digit (1) from the dividend and append it to 8, then repeat: 81 / 21

Step 2:
81 divided by 21 is 3 with a remainder of 18.
The next digit of our result is 3. 
Result so far: 3.0
If we subtract 63 from 81, we get 18.
Append the next digit (3) from the dividend to 18 and continue with: 183 / 21

Moving on to step 3:
If we divide 183 by 21, we get 8 and a remainder of 15.
The number 8 becomes the next digit in our result. 
Result so far: 38.0
Subtract 168 from 183 to get 15.
Take the next digit (5) from the dividend and append it to 15, then repeat: 155 / 21

Advancing to step 4:
155 divided by 21 is 7 with a remainder of 8.
Write down 7 as next digit of the result. 
Result so far: 387.0
Deduct 147 from 155 and we're left with 8.
Fetch the next digit (8) from the dividend, attach it to 8 and continue: 88 / 21

Moving on to step 5:
If we divide 88 by 21, we get 4 and a remainder of 4.
Use 4 as the next digit of our solution. 
Result so far: 3874.0
Subtracting 84 from 88 leaves us with 4.
Fetch the next digit (7) from the dividend, attach it to 4 and continue: 47 / 21

Moving on to step 6:
21 goes into 47 2 times with a remainder of 5.
Put 2 as the next digit of the answer. 
Result so far: 38742.0
Deduct 42 from 47 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 7:
If we divide 50 by 21, we get 2 and a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 38742.2
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 8:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 38742.23
If we take 63 away from 80, we end up with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

On to step 9:
170 divided by 21 is 8 with a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 38742.238
Subtract 168 from 170 to get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Let's proceed to step 10:
21 goes into 20 0 times with a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 38742.238
Deduct 0 from 20 and we're left with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

On to step 11:
21 can be fit into 200 9 times, resulting in a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 38742.23809
Subtract 189 from 200 to get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 12:
21 goes into 110 5 times with a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 38742.238095
If we subtract 105 from 110, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 13:
When dividing 50 by 21, we get 2 with a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 38742.2380952
Deduct 42 from 50 and we're left with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Step 14:
The number 21 fits into 80 3 times, leaving a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 38742.23809523
Subtract 63 from 80 to get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

After the division, we end up with 38742.23809523 and a remainder of 1.7e-08.