We're dividing 525018 by 21 
The aim is to understand the frequency of 21 in 525018.

Advancing to step 1:
21 can be fit into 5 0 times, resulting in a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 5, we end up with 5.
Bring next digit (2) of the dividend behind the 5 and repeat the process: 52 / 21

Let's proceed to step 2:
When dividing 52 by 21, we get 2 with a remainder of 10.
Put 2 as the next digit of the answer. 
Result so far: 2.0
Subtract 42 from 52 to get 10.
Grab the next digit (5) from the dividend, add it to 10, then carry on: 105 / 21

Advancing to step 3:
105 divided by 21 is 5 with a remainder of 0.
Write down 5 as next digit of the result. 
Result so far: 25.0
The remainder is 0 after subtracting 105 from 105.
Fetch the next digit (0) from the dividend, attach it to 0 and continue: 0 / 21

Advancing to step 4:
0 divided by 21 is 0 with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 250.0
If we subtract 0 from 0, we get 0.
Take the next digit (1) from the dividend and append it to 0, then repeat: 1 / 21

Step 5:
1 divided by 21 is 0 with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 2500.0
If we subtract 0 from 1, we get 1.
Fetch the next digit (8) from the dividend, attach it to 1 and continue: 18 / 21

Let's proceed to step 6:
18 divided by 21 is 0 with a remainder of 18.
Put 0 as the next digit of the answer. 
Result so far: 25000.0
If we take 0 away from 18, we end up 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 7:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 25000.8
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.

Advancing to step 8:
21 goes into 120 5 times with a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 25000.85
Deduct 105 from 120 and we're left 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.

Moving on to step 9:
If we divide 150 by 21, we get 7 and a remainder of 3.
The next digit of our result is 7. 
Result so far: 25000.857
Deduct 147 from 150 and we're left 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.

Moving on to step 10:
21 can be fit into 30 1 times, resulting in a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 25000.8571
Deduct 21 from 30 and we're left with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Going ahead to step 11:
21 goes into 90 4 times with a remainder of 6.
The next digit of our result is 4. 
Result so far: 25000.85714
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 12:
60 divided by 21 is 2 with a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 25000.857142
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.

Step 13:
21 can be fit into 180 8 times, resulting in a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 25000.8571428
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 14:
If we divide 120 by 21, we get 5 and a remainder of 15.
The next digit of our result is 5. 
Result so far: 25000.85714285
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.

Our division results in 25000.85714285 with a remaining 1.5e-08.