We look at the division of 156585 by 21 
The aim is to understand the frequency of 21 in 156585.

Moving on to step 1:
When dividing 1 by 21, we get 0 with a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Include the next digit (5) from the dividend after 1, then repeat: 15 / 21

Advancing to step 2:
15 divided by 21 is 0 with a remainder of 15.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 15 after subtracting 0 from 15.
Bring next digit (6) of the dividend behind the 15 and repeat the process: 156 / 21

Moving on to step 3:
The number 21 fits into 156 7 times, leaving a remainder of 9.
Write down 7 as next digit of the result. 
Result so far: 7.0
Subtract 147 from 156 to get 9.
Take the next digit (5) from the dividend and append it to 9, then repeat: 95 / 21

Going ahead to step 4:
The number 21 fits into 95 4 times, leaving a remainder of 11.
The next digit of our result is 4. 
Result so far: 74.0
If we take 84 away from 95, we end up with 11.
Grab the next digit (8) from the dividend, add it to 11, then carry on: 118 / 21

Moving on to step 5:
21 can be fit into 118 5 times, resulting in a remainder of 13.
Put 5 as the next digit of the answer. 
Result so far: 745.0
If we subtract 105 from 118, we get 13.
Take the next digit (5) from the dividend and append it to 13, then repeat: 135 / 21

Let's proceed to step 6:
21 can be fit into 135 6 times, resulting in a remainder of 9.
Use 6 as the next digit of our solution. 
Result so far: 7456.0
The remainder is 9 after subtracting 126 from 135.
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 7:
90 divided by 21 is 4 with a remainder of 6.
Use 4 as the next digit of our solution. 
Result so far: 7456.4
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.

Going ahead to step 8:
If we divide 60 by 21, we get 2 and a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 7456.42
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.

Advancing to step 9:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 7456.428
If we take 168 away from 180, we end up 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.

On to step 10:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 7456.4285
Subtracting 105 from 120 leaves us 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 11:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 7456.42857
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.

Step 12:
21 can be fit into 30 1 times, resulting in a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 7456.428571
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.

Moving on to step 13:
If we divide 90 by 21, we get 4 and a remainder of 6.
The next digit of our result is 4. 
Result so far: 7456.4285714
Subtracting 84 from 90 leaves us 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 14:
21 goes into 60 2 times with a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 7456.42857142
The remainder is 18 after subtracting 42 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

The final outcome is 7456.42857142, with a leftover of 1.8e-08.