We divide 789720 by 21
The aim is to understand the frequency of 21 in 789720.

Advancing to step 1:
When dividing 7 by 21, we get 0 with a remainder of 7.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Take the next digit (8) from the dividend and append it to 7, then repeat: 78 / 21

Going ahead to step 2:
78 divided by 21 is 3 with a remainder of 15.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
Deduct 63 from 78 and we're left with 15.
Take the next digit (9) from the dividend and append it to 15, then repeat: 159 / 21

Moving on to step 3:
When dividing 159 by 21, we get 7 with a remainder of 12.
Put 7 as the next digit of the answer. 
Result so far: 37.0
Subtracting 147 from 159 leaves us with 12.
Include the next digit (7) from the dividend after 12, then repeat: 127 / 21

Step 4:
21 goes into 127 6 times with a remainder of 1.
Put 6 as the next digit of the answer. 
Result so far: 376.0
If we take 126 away from 127, we end up with 1.
Fetch the next digit (2) from the dividend, attach it to 1 and continue: 12 / 21

Step 5:
If we divide 12 by 21, we get 0 and a remainder of 12.
The number 0 becomes the next digit in our result. 
Result so far: 3760.0
Subtract 0 from 12 to get 12.
Append the next digit (0) from the dividend to 12 and continue with: 120 / 21

Going ahead to step 6:
If we divide 120 by 21, we get 5 and a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 37605.0
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.

On to step 7:
The number 21 fits into 150 7 times, leaving a remainder of 3.
Put 7 as the next digit of the answer. 
Result so far: 37605.7
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 8:
30 divided by 21 is 1 with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 37605.71
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.

Step 9:
21 goes into 90 4 times with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 37605.714
Deduct 84 from 90 and we're left 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 10:
When dividing 60 by 21, we get 2 with a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 37605.7142
Subtracting 42 from 60 leaves us 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.

On to step 11:
21 goes into 180 8 times with a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 37605.71428
If we take 168 away from 180, we end up 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.

On to step 12:
The number 21 fits into 120 5 times, leaving a remainder of 15.
The next digit of our result is 5. 
Result so far: 37605.714285
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.

Advancing to step 13:
150 divided by 21 is 7 with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 37605.7142857
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 14:
When dividing 30 by 21, we get 1 with a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 37605.71428571
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

The quotient of the division is 37605.71428571, and the remainder is 9e-09.