212090 ÷ 21 
Let's see how many times 21 fits into 212090.

Advancing to step 1:
21 can be fit into 2 0 times, resulting in a remainder of 2.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 2, we get 2.
Include the next digit (1) from the dividend after 2, then repeat: 21 / 21

Step 2:
21 can be fit into 21 1 times, resulting in a remainder of 0.
Use 1 as the next digit of our solution. 
Result so far: 1.0
Subtract 21 from 21 to get 0.
Bring next digit (2) of the dividend behind the 0 and repeat the process: 2 / 21

Advancing to step 3:
2 divided by 21 is 0 with a remainder of 2.
Use 0 as the next digit of our solution. 
Result so far: 10.0
The remainder is 2 after subtracting 0 from 2.
Take the next digit (0) from the dividend and append it to 2, then repeat: 20 / 21

Step 4:
21 can be fit into 20 0 times, resulting in a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 100.0
If we subtract 0 from 20, we get 20.
Fetch the next digit (9) from the dividend, attach it to 20 and continue: 209 / 21

Let's proceed to step 5:
21 goes into 209 9 times with a remainder of 20.
The next digit of our result is 9. 
Result so far: 1009.0
Deduct 189 from 209 and we're left with 20.
Append the next digit (0) from the dividend to 20 and continue with: 200 / 21

Moving on to step 6:
The number 21 fits into 200 9 times, leaving a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 10099.0
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

On to step 7:
21 can be fit into 110 5 times, resulting in a remainder of 5.
The number 5 becomes the next digit in our result. 
Result so far: 10099.5
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 8:
21 can be fit into 50 2 times, resulting in a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 10099.52
If we subtract 42 from 50, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 9:
21 goes into 80 3 times with a remainder of 17.
The next digit of our result is 3. 
Result so far: 10099.523
The remainder is 17 after subtracting 63 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Let's proceed to step 10:
21 can be fit into 170 8 times, resulting in a remainder of 2.
The next digit of our result is 8. 
Result so far: 10099.5238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 11:
When dividing 20 by 21, we get 0 with a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 10099.5238
If we subtract 0 from 20, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 12:
200 divided by 21 is 9 with a remainder of 11.
The next digit of our result is 9. 
Result so far: 10099.523809
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

On to step 13:
When dividing 110 by 21, we get 5 with a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 10099.5238095
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 14:
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: 10099.52380952
Subtract 42 from 50 to get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

After the division, we end up with 10099.52380952 and a remainder of 8e-09.