403591 ÷ 21 
We want to divide 403591 by 21.

Step 1:
If we divide 4 by 21, we get 0 and a remainder of 4.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 4, we get 4.
Append the next digit (0) from the dividend to 4 and continue with: 40 / 21

Let's proceed to step 2:
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: 1.0
If we take 21 away from 40, we end up with 19.
Bring next digit (3) of the dividend behind the 19 and repeat the process: 193 / 21

Advancing to step 3:
When dividing 193 by 21, we get 9 with a remainder of 4.
The next digit of our result is 9. 
Result so far: 19.0
Subtracting 189 from 193 leaves us with 4.
Fetch the next digit (5) from the dividend, attach it to 4 and continue: 45 / 21

Step 4:
The number 21 fits into 45 2 times, leaving a remainder of 3.
Record the quotient 2 as the next digit in the result. 
Result so far: 192.0
The remainder is 3 after subtracting 42 from 45.
Bring next digit (9) of the dividend behind the 3 and repeat the process: 39 / 21

Moving on to step 5:
When dividing 39 by 21, we get 1 with a remainder of 18.
Record the quotient 1 as the next digit in the result. 
Result so far: 1921.0
If we subtract 21 from 39, we get 18.
Bring next digit (1) of the dividend behind the 18 and repeat the process: 181 / 21

Advancing to step 6:
If we divide 181 by 21, we get 8 and a remainder of 13.
Write down 8 as next digit of the result. 
Result so far: 19218.0
The remainder is 13 after subtracting 168 from 181.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 7:
The number 21 fits into 130 6 times, leaving a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 19218.6
Subtract 126 from 130 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 8:
When dividing 40 by 21, we get 1 with a remainder of 19.
Write down 1 as next digit of the result. 
Result so far: 19218.61
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.

Let's proceed to step 9:
190 divided by 21 is 9 with a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 19218.619
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.

Moving on to step 10:
When dividing 10 by 21, we get 0 with a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 19218.619
The remainder is 10 after subtracting 0 from 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Let's proceed to step 11:
The number 21 fits into 100 4 times, leaving a remainder of 16.
The next digit of our result is 4. 
Result so far: 19218.61904
If we take 84 away from 100, we end up with 16.
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 12:
If we divide 160 by 21, we get 7 and a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 19218.619047
Subtract 147 from 160 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Moving on to step 13:
The number 21 fits into 130 6 times, leaving a remainder of 4.
The next digit of our result is 6. 
Result so far: 19218.6190476
The remainder is 4 after subtracting 126 from 130.
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 14:
When dividing 40 by 21, we get 1 with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 19218.61904761
If we subtract 21 from 40, we 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.

In conclusion, the division gives 19218.61904761 with a balance of 1.9e-08.