212364 ÷ 21 
We want to figure out the number of times 212364 can be divided by 21.

Step 1:
When dividing 2 by 21, we get 0 with a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 2, we get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 21

Going ahead to step 2:
21 divided by 21 is 1 with a remainder of 0.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
Subtracting 21 from 21 leaves us with 0.
Bring next digit (2) of the dividend behind the 0 and repeat the process: 2 / 21

Let's proceed to step 3:
If we divide 2 by 21, we get 0 and a remainder of 2.
The number 0 becomes the next digit in our result. 
Result so far: 10.0
Subtracting 0 from 2 leaves us with 2.
Grab the next digit (3) from the dividend, add it to 2, then carry on: 23 / 21

On to step 4:
21 goes into 23 1 times with a remainder of 2.
The number 1 becomes the next digit in our result. 
Result so far: 101.0
The remainder is 2 after subtracting 21 from 23.
Include the next digit (6) from the dividend after 2, then repeat: 26 / 21

Step 5:
The number 21 fits into 26 1 times, leaving a remainder of 5.
The next digit of our result is 1. 
Result so far: 1011.0
Subtracting 21 from 26 leaves us with 5.
Append the next digit (4) from the dividend to 5 and continue with: 54 / 21

Advancing to step 6:
54 divided by 21 is 2 with a remainder of 12.
Put 2 as the next digit of the answer. 
Result so far: 10112.0
Subtract 42 from 54 to 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 7:
The number 21 fits into 120 5 times, leaving a remainder of 15.
The next digit of our result is 5. 
Result so far: 10112.5
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.

On to step 8:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 10112.57
Subtracting 147 from 150 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 9:
When dividing 30 by 21, we get 1 with a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 10112.571
If we subtract 21 from 30, we get 9.
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:
21 can be fit into 90 4 times, resulting in a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 10112.5714
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 11:
21 goes into 60 2 times with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 10112.57142
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.

On to step 12:
21 goes into 180 8 times with a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 10112.571428
The remainder is 12 after subtracting 168 from 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Let's proceed to step 13:
120 divided by 21 is 5 with a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 10112.5714285
Subtract 105 from 120 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Going ahead to step 14:
21 goes into 150 7 times with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 10112.57142857
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.

The final outcome is 10112.57142857, with a leftover of 3e-09.