838557 divided by 21 
The aim is to understand the frequency of 21 in 838557.

Advancing to step 1:
21 goes into 8 0 times with a remainder of 8.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 8 to get 8.
Bring next digit (3) of the dividend behind the 8 and repeat the process: 83 / 21

On to step 2:
If we divide 83 by 21, we get 3 and a remainder of 20.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
Subtract 63 from 83 to get 20.
Append the next digit (8) from the dividend to 20 and continue with: 208 / 21

Advancing to step 3:
208 divided by 21 is 9 with a remainder of 19.
Record the quotient 9 as the next digit in the result. 
Result so far: 39.0
Subtracting 189 from 208 leaves us with 19.
Fetch the next digit (5) from the dividend, attach it to 19 and continue: 195 / 21

Let's proceed to step 4:
When dividing 195 by 21, we get 9 with a remainder of 6.
Record the quotient 9 as the next digit in the result. 
Result so far: 399.0
If we take 189 away from 195, we end up with 6.
Include the next digit (5) from the dividend after 6, then repeat: 65 / 21

Moving on to step 5:
When dividing 65 by 21, we get 3 with a remainder of 2.
Record the quotient 3 as the next digit in the result. 
Result so far: 3993.0
Deduct 63 from 65 and we're left with 2.
Append the next digit (7) from the dividend to 2 and continue with: 27 / 21

Advancing to step 6:
The number 21 fits into 27 1 times, leaving a remainder of 6.
The next digit of our result is 1. 
Result so far: 39931.0
If we take 21 away from 27, we end up 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 7:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 39931.2
If we take 42 away from 60, 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 8:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 39931.28
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 9:
When dividing 120 by 21, we get 5 with a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 39931.285
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.

Step 10:
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: 39931.2857
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.

Advancing to step 11:
21 goes into 30 1 times with a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 39931.28571
If we take 21 away from 30, we end up 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.

On to step 12:
When dividing 90 by 21, we get 4 with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 39931.285714
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.

Moving on to step 13:
If we divide 60 by 21, we get 2 and a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 39931.2857142
If we take 42 away from 60, 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.

Moving on to step 14:
When dividing 180 by 21, we get 8 with a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 39931.28571428
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.

The quotient of the division is 39931.28571428, and the remainder is 1.2e-08.