800528 ÷ 21 
The aim is to understand the frequency of 21 in 800528.

Going ahead to step 1:
When dividing 8 by 21, we get 0 with a remainder of 8.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 8, we get 8.
Append the next digit (0) from the dividend to 8 and continue with: 80 / 21

Step 2:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 3.0
If we take 63 away from 80, we end up with 17.
Include the next digit (0) from the dividend after 17, then repeat: 170 / 21

Advancing to step 3:
21 can be fit into 170 8 times, resulting in a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 38.0
If we subtract 168 from 170, we get 2.
Grab the next digit (5) from the dividend, add it to 2, then carry on: 25 / 21

Moving on to step 4:
If we divide 25 by 21, we get 1 and a remainder of 4.
Use 1 as the next digit of our solution. 
Result so far: 381.0
Subtracting 21 from 25 leaves us with 4.
Grab the next digit (2) from the dividend, add it to 4, then carry on: 42 / 21

Going ahead to step 5:
The number 21 fits into 42 2 times, leaving a remainder of 0.
Record the quotient 2 as the next digit in the result. 
Result so far: 3812.0
Deduct 42 from 42 and we're left with 0.
Fetch the next digit (8) from the dividend, attach it to 0 and continue: 8 / 21

Step 6:
When dividing 8 by 21, we get 0 with a remainder of 8.
Use 0 as the next digit of our solution. 
Result so far: 38120.0
The remainder is 8 after subtracting 0 from 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Advancing to step 7:
80 divided by 21 is 3 with a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 38120.3
Subtract 63 from 80 to get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Step 8:
21 goes into 170 8 times with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 38120.38
Deduct 168 from 170 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 9:
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: 38120.38
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 10:
If we divide 200 by 21, we get 9 and a remainder of 11.
Use 9 as the next digit of our solution. 
Result so far: 38120.3809
Subtract 189 from 200 to get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Moving on to step 11:
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: 38120.38095
Deduct 105 from 110 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 12:
21 can be fit into 50 2 times, resulting in a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 38120.380952
If we take 42 away from 50, we end up with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Let's proceed to step 13:
If we divide 80 by 21, we get 3 and a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 38120.3809523
If we take 63 away from 80, we end up with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Going ahead to step 14:
If we divide 170 by 21, we get 8 and a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 38120.38095238
Deduct 168 from 170 and we're left with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

After the division, we end up with 38120.38095238 and a remainder of 2e-09.