We're dividing 161984 by 21 
The aim is to understand the frequency of 21 in 161984.

Let's proceed to step 1:
If we divide 1 by 21, we get 0 and a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Include the next digit (6) from the dividend after 1, then repeat: 16 / 21

Going ahead to step 2:
The number 21 fits into 16 0 times, leaving a remainder of 16.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 16 after subtracting 0 from 16.
Grab the next digit (1) from the dividend, add it to 16, then carry on: 161 / 21

Step 3:
If we divide 161 by 21, we get 7 and a remainder of 14.
Put 7 as the next digit of the answer. 
Result so far: 7.0
If we subtract 147 from 161, we get 14.
Grab the next digit (9) from the dividend, add it to 14, then carry on: 149 / 21

Advancing to step 4:
When dividing 149 by 21, we get 7 with a remainder of 2.
Use 7 as the next digit of our solution. 
Result so far: 77.0
If we subtract 147 from 149, we get 2.
Append the next digit (8) from the dividend to 2 and continue with: 28 / 21

Going ahead to step 5:
If we divide 28 by 21, we get 1 and a remainder of 7.
Use 1 as the next digit of our solution. 
Result so far: 771.0
Subtracting 21 from 28 leaves us with 7.
Grab the next digit (4) from the dividend, add it to 7, then carry on: 74 / 21

Going ahead to step 6:
21 goes into 74 3 times with a remainder of 11.
Record the quotient 3 as the next digit in the result. 
Result so far: 7713.0
Deduct 63 from 74 and we're left with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Let's proceed to step 7:
21 goes into 110 5 times with a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 7713.5
Subtract 105 from 110 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Let's proceed to step 8:
If we divide 50 by 21, we get 2 and a remainder of 8.
The next digit of our result is 2. 
Result so far: 7713.52
If we take 42 away from 50, we end up with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 9:
When dividing 80 by 21, we get 3 with a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 7713.523
The remainder is 17 after subtracting 63 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Advancing to step 10:
170 divided by 21 is 8 with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 7713.5238
Subtract 168 from 170 to get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 11:
21 goes into 20 0 times with a remainder of 20.
The next digit of our result is 0. 
Result so far: 7713.5238
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 12:
21 can be fit into 200 9 times, resulting in a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 7713.523809
The remainder is 11 after subtracting 189 from 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

On to step 13:
The number 21 fits into 110 5 times, leaving a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 7713.5238095
Deduct 105 from 110 and we're left with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

On to step 14:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 7713.52380952
Subtracting 42 from 50 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Our division results in 7713.52380952 with a remaining 8e-09.