We look at the division of 41216506 by 21 
The aim is to understand the frequency of 21 in 41216506.

Going ahead to step 1:
If we divide 4 by 21, we get 0 and a remainder of 4.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 4, we end up with 4.
Include the next digit (1) from the dividend after 4, then repeat: 41 / 21

On to step 2:
21 can be fit into 41 1 times, resulting in a remainder of 20.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Subtract 21 from 41 to get 20.
Take the next digit (2) from the dividend and append it to 20, then repeat: 202 / 21

Going ahead to step 3:
21 can be fit into 202 9 times, resulting in a remainder of 13.
Use 9 as the next digit of our solution. 
Result so far: 19.0
Deduct 189 from 202 and we're left with 13.
Fetch the next digit (1) from the dividend, attach it to 13 and continue: 131 / 21

On to step 4:
The number 21 fits into 131 6 times, leaving a remainder of 5.
Write down 6 as next digit of the result. 
Result so far: 196.0
Subtract 126 from 131 to get 5.
Include the next digit (6) from the dividend after 5, then repeat: 56 / 21

Going ahead to step 5:
56 divided by 21 is 2 with a remainder of 14.
The next digit of our result is 2. 
Result so far: 1962.0
Subtracting 42 from 56 leaves us with 14.
Append the next digit (5) from the dividend to 14 and continue with: 145 / 21

Advancing to step 6:
The number 21 fits into 145 6 times, leaving a remainder of 19.
The next digit of our result is 6. 
Result so far: 19626.0
Deduct 126 from 145 and we're left with 19.
Fetch the next digit (0) from the dividend, attach it to 19 and continue: 190 / 21

Step 7:
If we divide 190 by 21, we get 9 and a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 196269.0
If we subtract 189 from 190, we get 1.
Grab the next digit (6) from the dividend, add it to 1, then carry on: 16 / 21

Moving on to step 8:
If we divide 16 by 21, we get 0 and a remainder of 16.
Put 0 as the next digit of the answer. 
Result so far: 1962690.0
If we subtract 0 from 16, 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.

Going ahead to step 9:
If we divide 160 by 21, we get 7 and a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 1962690.7
Subtract 147 from 160 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 10:
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: 1962690.76
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.

Step 11:
When dividing 40 by 21, we get 1 with a remainder of 19.
Use 1 as the next digit of our solution. 
Result so far: 1962690.761
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.

Step 12:
21 goes into 190 9 times with a remainder of 1.
The number 9 becomes the next digit in our result. 
Result so far: 1962690.7619
If we subtract 189 from 190, we get 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 13:
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: 1962690.7619
Subtracting 0 from 10 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Going ahead to step 14:
21 goes into 100 4 times with a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 1962690.761904
Subtracting 84 from 100 leaves us with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

On to step 15:
The number 21 fits into 160 7 times, leaving a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 1962690.7619047
If we subtract 147 from 160, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Moving on to step 16:
When dividing 130 by 21, we get 6 with a remainder of 4.
Record the quotient 6 as the next digit in the result. 
Result so far: 1962690.76190476
The remainder is 4 after subtracting 126 from 130.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

The final result is 1962690.76190476 with a remainder of 4e-09.