73487 ÷ 21 
The aim is to understand the frequency of 21 in 73487.

Going ahead to step 1:
The number 21 fits into 7 0 times, leaving a remainder of 7.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 7 to get 7.
Append the next digit (3) from the dividend to 7 and continue with: 73 / 21

Let's proceed to step 2:
21 goes into 73 3 times with a remainder of 10.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Deduct 63 from 73 and we're left with 10.
Append the next digit (4) from the dividend to 10 and continue with: 104 / 21

Moving on to step 3:
104 divided by 21 is 4 with a remainder of 20.
Record the quotient 4 as the next digit in the result. 
Result so far: 34.0
The remainder is 20 after subtracting 84 from 104.
Include the next digit (8) from the dividend after 20, then repeat: 208 / 21

On to step 4:
The number 21 fits into 208 9 times, leaving a remainder of 19.
Record the quotient 9 as the next digit in the result. 
Result so far: 349.0
Subtract 189 from 208 to get 19.
Append the next digit (7) from the dividend to 19 and continue with: 197 / 21

Moving on to step 5:
If we divide 197 by 21, we get 9 and a remainder of 8.
Use 9 as the next digit of our solution. 
Result so far: 3499.0
If we take 189 away from 197, 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.

Step 6:
If we divide 80 by 21, we get 3 and a remainder of 17.
Write down 3 as next digit of the result. 
Result so far: 3499.3
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.

Going ahead to step 7:
When dividing 170 by 21, we get 8 with a remainder of 2.
Use 8 as the next digit of our solution. 
Result so far: 3499.38
If we take 168 away from 170, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 8:
The number 21 fits into 20 0 times, leaving a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 3499.38
The remainder is 20 after subtracting 0 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Advancing to step 9:
When dividing 200 by 21, we get 9 with a remainder of 11.
Record the quotient 9 as the next digit in the result. 
Result so far: 3499.3809
Subtract 189 from 200 to get 11.
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 10:
21 can be fit into 110 5 times, resulting in a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 3499.38095
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.

Step 11:
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: 3499.380952
Deduct 42 from 50 and we're left 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.

On to step 12:
If we divide 80 by 21, we get 3 and a remainder of 17.
Record the quotient 3 as the next digit in the result. 
Result so far: 3499.3809523
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.

On to step 13:
21 goes into 170 8 times with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 3499.38095238
Subtracting 168 from 170 leaves us with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

After the division, we end up with 3499.38095238 and a remainder of 2e-09.