We're dividing 210595 by 21 
The aim is to understand the frequency of 21 in 210595.

Going ahead to step 1:
2 divided by 21 is 0 with a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 2 after subtracting 0 from 2.
Take the next digit (1) from the dividend and append it to 2, then repeat: 21 / 21

Advancing to step 2:
When dividing 21 by 21, we get 1 with a remainder of 0.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
If we subtract 21 from 21, we get 0.
Append the next digit (0) from the dividend to 0 and continue with: 0 / 21

Moving on to step 3:
When dividing 0 by 21, we get 0 with a remainder of 0.
The next digit of our result is 0. 
Result so far: 10.0
Subtract 0 from 0 to get 0.
Grab the next digit (5) from the dividend, add it to 0, then carry on: 5 / 21

Moving on to step 4:
If we divide 5 by 21, we get 0 and a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 100.0
Deduct 0 from 5 and we're left with 5.
Bring next digit (9) of the dividend behind the 5 and repeat the process: 59 / 21

Moving on to step 5:
59 divided by 21 is 2 with a remainder of 17.
The next digit of our result is 2. 
Result so far: 1002.0
Subtract 42 from 59 to get 17.
Append the next digit (5) from the dividend to 17 and continue with: 175 / 21

Moving on to step 6:
When dividing 175 by 21, we get 8 with a remainder of 7.
The next digit of our result is 8. 
Result so far: 10028.0
Deduct 168 from 175 and we're left with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Going ahead to step 7:
70 divided by 21 is 3 with a remainder of 7.
Record the quotient 3 as the next digit in the result. 
Result so far: 10028.3
The remainder is 7 after subtracting 63 from 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Step 8:
21 can be fit into 70 3 times, resulting in a remainder of 7.
Use 3 as the next digit of our solution. 
Result so far: 10028.33
If we subtract 63 from 70, we get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

The final outcome is 10028.33, with a leftover of 0.007.