We're dividing 402589 by 21 
Let's see how many times 21 fits into 402589.

Going ahead to step 1:
When dividing 4 by 21, we get 0 with a remainder of 4.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 4 and we're left with 4.
Grab the next digit (0) from the dividend, add it to 4, then carry on: 40 / 21

On to step 2:
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: 1.0
Subtracting 21 from 40 leaves us with 19.
Bring next digit (2) of the dividend behind the 19 and repeat the process: 192 / 21

Let's proceed to step 3:
192 divided by 21 is 9 with a remainder of 3.
Write down 9 as next digit of the result. 
Result so far: 19.0
If we take 189 away from 192, we end up with 3.
Bring next digit (5) of the dividend behind the 3 and repeat the process: 35 / 21

Let's proceed to step 4:
If we divide 35 by 21, we get 1 and a remainder of 14.
Write down 1 as next digit of the result. 
Result so far: 191.0
Subtract 21 from 35 to get 14.
Take the next digit (8) from the dividend and append it to 14, then repeat: 148 / 21

Advancing to step 5:
The number 21 fits into 148 7 times, leaving a remainder of 1.
Use 7 as the next digit of our solution. 
Result so far: 1917.0
Subtracting 147 from 148 leaves us with 1.
Bring next digit (9) of the dividend behind the 1 and repeat the process: 19 / 21

Let's proceed to step 6:
19 divided by 21 is 0 with a remainder of 19.
Write down 0 as next digit of the result. 
Result so far: 19170.0
If we take 0 away from 19, 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.

Advancing to step 7:
When dividing 190 by 21, we get 9 with a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 19170.9
Subtract 189 from 190 to 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.

On to step 8:
21 goes into 10 0 times with a remainder of 10.
Record the quotient 0 as the next digit in the result. 
Result so far: 19170.9
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 9:
If we divide 100 by 21, we get 4 and a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 19170.904
Subtracting 84 from 100 leaves us 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.

On to step 10:
21 can be fit into 160 7 times, resulting in a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 19170.9047
If we subtract 147 from 160, we 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.

On to step 11:
21 goes into 130 6 times with a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 19170.90476
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.

On to step 12:
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: 19170.904761
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.

Moving on to step 13:
21 can be fit into 190 9 times, resulting in a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 19170.9047619
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 14:
When dividing 10 by 21, we get 0 with a remainder of 10.
The next digit of our result is 0. 
Result so far: 19170.9047619
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.

Our division results in 19170.9047619 with a remaining 1e-08.