175597 ÷ 21 
The aim is to understand the frequency of 21 in 175597.

Step 1:
The number 21 fits into 1 0 times, leaving 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.
Append the next digit (7) from the dividend to 1 and continue with: 17 / 21

Let's proceed to step 2:
When dividing 17 by 21, we get 0 with a remainder of 17.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 17, we get 17.
Grab the next digit (5) from the dividend, add it to 17, then carry on: 175 / 21

Advancing to step 3:
The number 21 fits into 175 8 times, leaving a remainder of 7.
Write down 8 as next digit of the result. 
Result so far: 8.0
If we subtract 168 from 175, we get 7.
Fetch the next digit (5) from the dividend, attach it to 7 and continue: 75 / 21

Moving on to step 4:
21 can be fit into 75 3 times, resulting in a remainder of 12.
Put 3 as the next digit of the answer. 
Result so far: 83.0
If we subtract 63 from 75, we get 12.
Bring next digit (9) of the dividend behind the 12 and repeat the process: 129 / 21

On to step 5:
21 goes into 129 6 times with a remainder of 3.
The number 6 becomes the next digit in our result. 
Result so far: 836.0
If we subtract 126 from 129, we get 3.
Append the next digit (7) from the dividend to 3 and continue with: 37 / 21

Advancing to step 6:
When dividing 37 by 21, we get 1 with a remainder of 16.
The number 1 becomes the next digit in our result. 
Result so far: 8361.0
Subtract 21 from 37 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.

Moving on to step 7:
When dividing 160 by 21, we get 7 with a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 8361.7
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.

Step 8:
21 can be fit into 130 6 times, resulting in a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 8361.76
If we subtract 126 from 130, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Let's proceed to step 9:
The number 21 fits into 40 1 times, leaving a remainder of 19.
The next digit of our result is 1. 
Result so far: 8361.761
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.

Moving on to step 10:
21 goes into 190 9 times with a remainder of 1.
Write down 9 as next digit of the result. 
Result so far: 8361.7619
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.

On to step 11:
If we divide 10 by 21, we get 0 and a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 8361.7619
Subtract 0 from 10 to get 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 12:
If we divide 100 by 21, we get 4 and a remainder of 16.
Write down 4 as next digit of the result. 
Result so far: 8361.761904
If we subtract 84 from 100, we 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.

Let's proceed to step 13:
21 goes into 160 7 times with a remainder of 13.
The next digit of our result is 7. 
Result so far: 8361.7619047
Subtracting 147 from 160 leaves us 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.

Going ahead to step 14:
130 divided by 21 is 6 with a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 8361.76190476
Deduct 126 from 130 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

After the division, we end up with 8361.76190476 and a remainder of 4e-09.