78083863 ÷ 21 
The aim is to understand the frequency of 21 in 78083863.

On to step 1:
The number 21 fits into 7 0 times, leaving a remainder of 7.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Include the next digit (8) from the dividend after 7, then repeat: 78 / 21

Step 2:
78 divided by 21 is 3 with a remainder of 15.
Write down 3 as next digit of the result. 
Result so far: 3.0
Subtracting 63 from 78 leaves us with 15.
Take the next digit (0) from the dividend and append it to 15, then repeat: 150 / 21

Going ahead to step 3:
21 goes into 150 7 times with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 37.0
Deduct 147 from 150 and we're left with 3.
Take the next digit (8) from the dividend and append it to 3, then repeat: 38 / 21

Let's proceed to step 4:
21 goes into 38 1 times with a remainder of 17.
The number 1 becomes the next digit in our result. 
Result so far: 371.0
Subtract 21 from 38 to get 17.
Bring next digit (3) of the dividend behind the 17 and repeat the process: 173 / 21

Going ahead to step 5:
173 divided by 21 is 8 with a remainder of 5.
Record the quotient 8 as the next digit in the result. 
Result so far: 3718.0
The remainder is 5 after subtracting 168 from 173.
Take the next digit (8) from the dividend and append it to 5, then repeat: 58 / 21

Moving on to step 6:
21 can be fit into 58 2 times, resulting in a remainder of 16.
Put 2 as the next digit of the answer. 
Result so far: 37182.0
If we subtract 42 from 58, we get 16.
Take the next digit (6) from the dividend and append it to 16, then repeat: 166 / 21

Going ahead to step 7:
The number 21 fits into 166 7 times, leaving a remainder of 19.
Put 7 as the next digit of the answer. 
Result so far: 371827.0
Subtract 147 from 166 to get 19.
Grab the next digit (3) from the dividend, add it to 19, then carry on: 193 / 21

Advancing to step 8:
193 divided by 21 is 9 with a remainder of 4.
Use 9 as the next digit of our solution. 
Result so far: 3718279.0
Deduct 189 from 193 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Going ahead to step 9:
21 can be fit into 40 1 times, resulting in a remainder of 19.
The next digit of our result is 1. 
Result so far: 3718279.1
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.

Step 10:
When dividing 190 by 21, we get 9 with a remainder of 1.
The number 9 becomes the next digit in our result. 
Result so far: 3718279.19
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 11:
10 divided by 21 is 0 with a remainder of 10.
Put 0 as the next digit of the answer. 
Result so far: 3718279.19
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.

Moving on to step 12:
21 can be fit into 100 4 times, resulting in a remainder of 16.
Write down 4 as next digit of the result. 
Result so far: 3718279.1904
Subtract 84 from 100 to 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.

Step 13:
When dividing 160 by 21, we get 7 with a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 3718279.19047
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.

Going ahead to step 14:
The number 21 fits into 130 6 times, leaving a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 3718279.190476
If we take 126 away from 130, we end up with 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 15:
21 can be fit into 40 1 times, resulting in a remainder of 19.
The next digit of our result is 1. 
Result so far: 3718279.1904761
If we subtract 21 from 40, we get 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 16:
21 can be fit into 190 9 times, resulting in a remainder of 1.
The number 9 becomes the next digit in our result. 
Result so far: 3718279.19047619
The remainder is 1 after subtracting 189 from 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Our division results in 3718279.19047619 with a remaining 1e-09.