402327 ÷ 21 
The aim is to understand the frequency of 21 in 402327.

Advancing to step 1:
The number 21 fits into 4 0 times, leaving a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we take 0 away from 4, we end up with 4.
Append the next digit (0) from the dividend to 4 and continue with: 40 / 21

Step 2:
21 can be fit into 40 1 times, resulting in a remainder of 19.
Use 1 as the next digit of our solution. 
Result so far: 1.0
Subtracting 21 from 40 leaves us with 19.
Take the next digit (2) from the dividend and append it to 19, then repeat: 192 / 21

Step 3:
192 divided by 21 is 9 with a remainder of 3.
Write down 9 as next digit of the result. 
Result so far: 19.0
If we take 189 away from 192, we end up with 3.
Include the next digit (3) from the dividend after 3, then repeat: 33 / 21

Going ahead to step 4:
21 can be fit into 33 1 times, resulting in a remainder of 12.
Write down 1 as next digit of the result. 
Result so far: 191.0
If we take 21 away from 33, we end up with 12.
Bring next digit (2) of the dividend behind the 12 and repeat the process: 122 / 21

Step 5:
21 can be fit into 122 5 times, resulting in a remainder of 17.
Use 5 as the next digit of our solution. 
Result so far: 1915.0
Subtract 105 from 122 to get 17.
Include the next digit (7) from the dividend after 17, then repeat: 177 / 21

Step 6:
21 can be fit into 177 8 times, resulting in a remainder of 9.
The next digit of our result is 8. 
Result so far: 19158.0
If we subtract 168 from 177, 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.

On to step 7:
90 divided by 21 is 4 with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 19158.4
Deduct 84 from 90 and we're left with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Let's proceed to step 8:
21 can be fit into 60 2 times, resulting in a remainder of 18.
The next digit of our result is 2. 
Result so far: 19158.42
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.

Let's proceed to step 9:
180 divided by 21 is 8 with a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 19158.428
Subtracting 168 from 180 leaves us 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 10:
The number 21 fits into 120 5 times, leaving a remainder of 15.
The next digit of our result is 5. 
Result so far: 19158.4285
The remainder is 15 after subtracting 105 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 11:
21 goes into 150 7 times with a remainder of 3.
The next digit of our result is 7. 
Result so far: 19158.42857
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.

Step 12:
The number 21 fits into 30 1 times, leaving a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 19158.428571
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.

Moving on to step 13:
21 goes into 90 4 times with a remainder of 6.
Put 4 as the next digit of the answer. 
Result so far: 19158.4285714
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 14:
If we divide 60 by 21, we get 2 and a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 19158.42857142
If we subtract 42 from 60, we 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.

After the division, we end up with 19158.42857142 and a remainder of 1.8e-08.