We're dividing 64708750 by 21 
The aim is to understand the frequency of 21 in 64708750.

Step 1:
When dividing 6 by 21, we get 0 with a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Take the next digit (4) from the dividend and append it to 6, then repeat: 64 / 21

Advancing to step 2:
21 goes into 64 3 times with a remainder of 1.
Use 3 as the next digit of our solution. 
Result so far: 3.0
If we take 63 away from 64, we end up with 1.
Take the next digit (7) from the dividend and append it to 1, then repeat: 17 / 21

Going ahead to step 3:
21 goes into 17 0 times with a remainder of 17.
The next digit of our result is 0. 
Result so far: 30.0
Subtracting 0 from 17 leaves us with 17.
Grab the next digit (0) from the dividend, add it to 17, then carry on: 170 / 21

Moving on to step 4:
When dividing 170 by 21, we get 8 with a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 308.0
Deduct 168 from 170 and we're left with 2.
Grab the next digit (8) from the dividend, add it to 2, then carry on: 28 / 21

On to step 5:
If we divide 28 by 21, we get 1 and a remainder of 7.
Record the quotient 1 as the next digit in the result. 
Result so far: 3081.0
If we take 21 away from 28, we end up with 7.
Fetch the next digit (7) from the dividend, attach it to 7 and continue: 77 / 21

On to step 6:
77 divided by 21 is 3 with a remainder of 14.
Put 3 as the next digit of the answer. 
Result so far: 30813.0
Subtract 63 from 77 to get 14.
Fetch the next digit (5) from the dividend, attach it to 14 and continue: 145 / 21

Going ahead to step 7:
If we divide 145 by 21, we get 6 and a remainder of 19.
Use 6 as the next digit of our solution. 
Result so far: 308136.0
If we take 126 away from 145, we end up with 19.
Fetch the next digit (0) from the dividend, attach it to 19 and continue: 190 / 21

Advancing to step 8:
21 can be fit into 190 9 times, resulting in a remainder of 1.
The next digit of our result is 9. 
Result so far: 3081369.0
Subtracting 189 from 190 leaves us 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.

Let's proceed to step 9:
10 divided by 21 is 0 with a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 3081369.0
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.

Moving on to step 10:
If we divide 100 by 21, we get 4 and a remainder of 16.
The number 4 becomes the next digit in our result. 
Result so far: 3081369.04
Subtract 84 from 100 to get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 11:
21 goes into 160 7 times with a remainder of 13.
Write down 7 as next digit of the result. 
Result so far: 3081369.047
If we take 147 away from 160, we end up with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Let's proceed to step 12:
The number 21 fits into 130 6 times, leaving a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 3081369.0476
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.

Going ahead to step 13:
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: 3081369.04761
Deduct 21 from 40 and we're left 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.

Step 14:
If we divide 190 by 21, we get 9 and a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 3081369.047619
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.

On to step 15:
10 divided by 21 is 0 with a remainder of 10.
The next digit of our result is 0. 
Result so far: 3081369.047619
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 16:
21 can be fit into 100 4 times, resulting in a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 3081369.04761904
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.

In conclusion, the division gives 3081369.04761904 with a balance of 1.6e-08.