We're dividing 560964 by 21 
The aim is to understand the frequency of 21 in 560964.

Let's proceed to step 1:
If we divide 5 by 21, we get 0 and a remainder of 5.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 5, we end up with 5.
Fetch the next digit (6) from the dividend, attach it to 5 and continue: 56 / 21

Step 2:
21 goes into 56 2 times with a remainder of 14.
The next digit of our result is 2. 
Result so far: 2.0
Deduct 42 from 56 and we're left with 14.
Fetch the next digit (0) from the dividend, attach it to 14 and continue: 140 / 21

Advancing to step 3:
If we divide 140 by 21, we get 6 and a remainder of 14.
Use 6 as the next digit of our solution. 
Result so far: 26.0
Deduct 126 from 140 and we're left with 14.
Bring next digit (9) of the dividend behind the 14 and repeat the process: 149 / 21

Let's proceed to step 4:
The number 21 fits into 149 7 times, leaving a remainder of 2.
The number 7 becomes the next digit in our result. 
Result so far: 267.0
Subtracting 147 from 149 leaves us with 2.
Bring next digit (6) of the dividend behind the 2 and repeat the process: 26 / 21

Going ahead to step 5:
26 divided by 21 is 1 with a remainder of 5.
The next digit of our result is 1. 
Result so far: 2671.0
The remainder is 5 after subtracting 21 from 26.
Bring next digit (4) of the dividend behind the 5 and repeat the process: 54 / 21

On to step 6:
When dividing 54 by 21, we get 2 with a remainder of 12.
The next digit of our result is 2. 
Result so far: 26712.0
The remainder is 12 after subtracting 42 from 54.
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:
When dividing 120 by 21, we get 5 with a remainder of 15.
The next digit of our result is 5. 
Result so far: 26712.5
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.

Advancing to step 8:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 26712.57
If we take 147 away from 150, we end up 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:
21 can be fit into 30 1 times, resulting in a remainder of 9.
The next digit of our result is 1. 
Result so far: 26712.571
Subtract 21 from 30 to 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.

Let's proceed to 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: 26712.5714
Subtract 84 from 90 to 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.

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: 26712.57142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Moving on to step 12:
21 can be fit into 180 8 times, resulting in a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 26712.571428
Deduct 168 from 180 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.

Going ahead to step 13:
21 goes into 120 5 times with a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 26712.5714285
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.

On to step 14:
When dividing 150 by 21, we get 7 with a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 26712.57142857
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.

The final outcome is 26712.57142857, with a leftover of 3e-09.