722731 divided by 21 
The aim is to understand the frequency of 21 in 722731.

On to step 1:
When dividing 7 by 21, we get 0 with a remainder of 7.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 7 and we're left with 7.
Include the next digit (2) from the dividend after 7, then repeat: 72 / 21

Let's proceed to step 2:
If we divide 72 by 21, we get 3 and a remainder of 9.
Write down 3 as next digit of the result. 
Result so far: 3.0
Deduct 63 from 72 and we're left with 9.
Fetch the next digit (2) from the dividend, attach it to 9 and continue: 92 / 21

On to step 3:
21 can be fit into 92 4 times, resulting in a remainder of 8.
The number 4 becomes the next digit in our result. 
Result so far: 34.0
The remainder is 8 after subtracting 84 from 92.
Fetch the next digit (7) from the dividend, attach it to 8 and continue: 87 / 21

Going ahead to step 4:
21 can be fit into 87 4 times, resulting in a remainder of 3.
Record the quotient 4 as the next digit in the result. 
Result so far: 344.0
Subtracting 84 from 87 leaves us with 3.
Append the next digit (3) from the dividend to 3 and continue with: 33 / 21

Going ahead to step 5:
If we divide 33 by 21, we get 1 and a remainder of 12.
Write down 1 as next digit of the result. 
Result so far: 3441.0
If we subtract 21 from 33, we get 12.
Fetch the next digit (1) from the dividend, attach it to 12 and continue: 121 / 21

On to step 6:
The number 21 fits into 121 5 times, leaving a remainder of 16.
Record the quotient 5 as the next digit in the result. 
Result so far: 34415.0
Subtracting 105 from 121 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.

Step 7:
The number 21 fits into 160 7 times, leaving a remainder of 13.
The next digit of our result is 7. 
Result so far: 34415.7
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 8:
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: 34415.76
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.

Let's proceed to step 9:
If we divide 40 by 21, we get 1 and a remainder of 19.
The next digit of our result is 1. 
Result so far: 34415.761
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.

Moving on to step 10:
21 can be fit into 190 9 times, resulting in a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 34415.7619
Subtract 189 from 190 to 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.

Moving on to step 11:
21 goes into 10 0 times with a remainder of 10.
Write down 0 as next digit of the result. 
Result so far: 34415.7619
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.

Advancing to step 12:
The number 21 fits into 100 4 times, leaving a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 34415.761904
If we take 84 away from 100, we end up 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 13:
160 divided by 21 is 7 with a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 34415.7619047
Deduct 147 from 160 and we're left with 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 14:
21 can be fit into 130 6 times, resulting in a remainder of 4.
The next digit of our result is 6. 
Result so far: 34415.76190476
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.

After the division, we end up with 34415.76190476 and a remainder of 4e-09.