We're dividing 637519 by 21 
The aim is to understand the frequency of 21 in 637519.

Let's proceed to step 1:
21 goes into 6 0 times with a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 6 and we're left with 6.
Grab the next digit (3) from the dividend, add it to 6, then carry on: 63 / 21

Moving on to step 2:
21 goes into 63 3 times with a remainder of 0.
Put 3 as the next digit of the answer. 
Result so far: 3.0
Subtract 63 from 63 to get 0.
Fetch the next digit (7) from the dividend, attach it to 0 and continue: 7 / 21

Moving on to step 3:
If we divide 7 by 21, we get 0 and a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 30.0
Subtracting 0 from 7 leaves us with 7.
Grab the next digit (5) from the dividend, add it to 7, then carry on: 75 / 21

Let's proceed to step 4:
75 divided by 21 is 3 with a remainder of 12.
Use 3 as the next digit of our solution. 
Result so far: 303.0
If we subtract 63 from 75, we get 12.
Include the next digit (1) from the dividend after 12, then repeat: 121 / 21

On to step 5:
The number 21 fits into 121 5 times, leaving a remainder of 16.
The number 5 becomes the next digit in our result. 
Result so far: 3035.0
The remainder is 16 after subtracting 105 from 121.
Grab the next digit (9) from the dividend, add it to 16, then carry on: 169 / 21

On to step 6:
169 divided by 21 is 8 with a remainder of 1.
Record the quotient 8 as the next digit in the result. 
Result so far: 30358.0
The remainder is 1 after subtracting 168 from 169.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Moving on to step 7:
21 goes into 10 0 times with a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 30358.0
If we take 0 away from 10, we end up 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.

Let's proceed to step 8:
The number 21 fits into 100 4 times, leaving a remainder of 16.
Use 4 as the next digit of our solution. 
Result so far: 30358.04
Deduct 84 from 100 and we're left 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.

Advancing to step 9:
When dividing 160 by 21, we get 7 with a remainder of 13.
Write down 7 as next digit of the result. 
Result so far: 30358.047
The remainder is 13 after subtracting 147 from 160.
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:
If we divide 130 by 21, we get 6 and a remainder of 4.
Write down 6 as next digit of the result. 
Result so far: 30358.0476
Subtract 126 from 130 to 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.

Advancing to step 11:
When dividing 40 by 21, we get 1 with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 30358.04761
If we take 21 away from 40, we end up 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.

Advancing to step 12:
The number 21 fits into 190 9 times, leaving a remainder of 1.
The number 9 becomes the next digit in our result. 
Result so far: 30358.047619
Deduct 189 from 190 and we're left 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.

Going ahead to step 13:
If we divide 10 by 21, we get 0 and a remainder of 10.
Put 0 as the next digit of the answer. 
Result so far: 30358.047619
Deduct 0 from 10 and we're left 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.

Step 14:
If we divide 100 by 21, we get 4 and a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 30358.04761904
Deduct 84 from 100 and we're left 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.

The final result is 30358.04761904 with a remainder of 1.6e-08.