637971 ÷ 21 
Our goal is to divide 637971 by 21.

Moving on to step 1:
6 divided by 21 is 0 with a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 6, we get 6.
Include the next digit (3) from the dividend after 6, then repeat: 63 / 21

Going ahead to step 2:
If we divide 63 by 21, we get 3 and a remainder of 0.
Use 3 as the next digit of our solution. 
Result so far: 3.0
The remainder is 0 after subtracting 63 from 63.
Take the next digit (7) from the dividend and append it to 0, then repeat: 7 / 21

Step 3:
21 can be fit into 7 0 times, resulting in a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 30.0
Subtracting 0 from 7 leaves us with 7.
Append the next digit (9) from the dividend to 7 and continue with: 79 / 21

Step 4:
79 divided by 21 is 3 with a remainder of 16.
Write down 3 as next digit of the result. 
Result so far: 303.0
Subtracting 63 from 79 leaves us with 16.
Include the next digit (7) from the dividend after 16, then repeat: 167 / 21

On to step 5:
21 can be fit into 167 7 times, resulting in a remainder of 20.
Write down 7 as next digit of the result. 
Result so far: 3037.0
If we subtract 147 from 167, we get 20.
Grab the next digit (1) from the dividend, add it to 20, then carry on: 201 / 21

Moving on to step 6:
The number 21 fits into 201 9 times, leaving a remainder of 12.
Use 9 as the next digit of our solution. 
Result so far: 30379.0
Deduct 189 from 201 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 7:
If we divide 120 by 21, we get 5 and a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 30379.5
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.

Advancing to step 8:
The number 21 fits into 150 7 times, leaving a remainder of 3.
The next digit of our result is 7. 
Result so far: 30379.57
The remainder is 3 after subtracting 147 from 150.
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 9:
The number 21 fits into 30 1 times, leaving a remainder of 9.
The next digit of our result is 1. 
Result so far: 30379.571
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.

Step 10:
When dividing 90 by 21, we get 4 with a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 30379.5714
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.

Let's proceed to step 11:
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: 30379.57142
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.

Advancing to step 12:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 30379.571428
If we subtract 168 from 180, we get 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 13:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 30379.5714285
If we take 105 away from 120, we end up 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.

Let's proceed to step 14:
If we divide 150 by 21, we get 7 and a remainder of 3.
The next digit of our result is 7. 
Result so far: 30379.57142857
If we subtract 147 from 150, we 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.

After the division, we end up with 30379.57142857 and a remainder of 3e-09.