We look at the division of 783871 by 21 
We're looking to find how many times 21 goes into 783871.

Going ahead to step 1:
21 can be fit into 7 0 times, resulting in a remainder of 7.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Take the next digit (8) from the dividend and append it to 7, then repeat: 78 / 21

On to step 2:
When dividing 78 by 21, we get 3 with a remainder of 15.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Deduct 63 from 78 and we're left with 15.
Grab the next digit (3) from the dividend, add it to 15, then carry on: 153 / 21

On to step 3:
21 goes into 153 7 times with a remainder of 6.
Put 7 as the next digit of the answer. 
Result so far: 37.0
Subtract 147 from 153 to get 6.
Fetch the next digit (8) from the dividend, attach it to 6 and continue: 68 / 21

Moving on to step 4:
21 can be fit into 68 3 times, resulting in a remainder of 5.
Use 3 as the next digit of our solution. 
Result so far: 373.0
If we subtract 63 from 68, we get 5.
Include the next digit (7) from the dividend after 5, then repeat: 57 / 21

Let's proceed to step 5:
57 divided by 21 is 2 with a remainder of 15.
The number 2 becomes the next digit in our result. 
Result so far: 3732.0
The remainder is 15 after subtracting 42 from 57.
Append the next digit (1) from the dividend to 15 and continue with: 151 / 21

Step 6:
21 can be fit into 151 7 times, resulting in a remainder of 4.
Write down 7 as next digit of the result. 
Result so far: 37327.0
If we take 147 away from 151, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 7:
40 divided by 21 is 1 with a remainder of 19.
The next digit of our result is 1. 
Result so far: 37327.1
Subtract 21 from 40 to get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Going ahead to step 8:
21 can be fit into 190 9 times, resulting in a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 37327.19
Deduct 189 from 190 and we're left with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Going ahead to step 9:
21 can be fit into 10 0 times, resulting in a remainder of 10.
The next digit of our result is 0. 
Result so far: 37327.19
If we subtract 0 from 10, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 10:
The number 21 fits into 100 4 times, leaving a remainder of 16.
The next digit of our result is 4. 
Result so far: 37327.1904
The remainder is 16 after subtracting 84 from 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Let's proceed to step 11:
21 can be fit into 160 7 times, resulting in a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 37327.19047
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 12:
If we divide 130 by 21, we get 6 and a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 37327.190476
Subtracting 126 from 130 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Let's proceed to step 13:
If we divide 40 by 21, we get 1 and a remainder of 19.
The next digit of our result is 1. 
Result so far: 37327.1904761
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 14:
The number 21 fits into 190 9 times, leaving a remainder of 1.
The number 9 becomes the next digit in our result. 
Result so far: 37327.19047619
If we subtract 189 from 190, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

In conclusion, the division gives 37327.19047619 with a balance of 1e-09.