166673 divided by 21 
The aim is to understand the frequency of 21 in 166673.

Moving on to step 1:
21 can be fit into 1 0 times, resulting in a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 1 leaves us with 1.
Append the next digit (6) from the dividend to 1 and continue with: 16 / 21

Step 2:
21 goes into 16 0 times with a remainder of 16.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 16 leaves us with 16.
Fetch the next digit (6) from the dividend, attach it to 16 and continue: 166 / 21

Moving on to step 3:
The number 21 fits into 166 7 times, leaving a remainder of 19.
The next digit of our result is 7. 
Result so far: 7.0
Deduct 147 from 166 and we're left with 19.
Append the next digit (6) from the dividend to 19 and continue with: 196 / 21

Going ahead to step 4:
If we divide 196 by 21, we get 9 and a remainder of 7.
The next digit of our result is 9. 
Result so far: 79.0
The remainder is 7 after subtracting 189 from 196.
Append the next digit (7) from the dividend to 7 and continue with: 77 / 21

Advancing to step 5:
If we divide 77 by 21, we get 3 and a remainder of 14.
Put 3 as the next digit of the answer. 
Result so far: 793.0
Subtract 63 from 77 to get 14.
Include the next digit (3) from the dividend after 14, then repeat: 143 / 21

On to step 6:
When dividing 143 by 21, we get 6 with a remainder of 17.
Put 6 as the next digit of the answer. 
Result so far: 7936.0
If we subtract 126 from 143, we get 17.
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 7:
When dividing 170 by 21, we get 8 with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 7936.8
If we subtract 168 from 170, we 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.

On to step 8:
21 goes into 20 0 times with a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 7936.8
Deduct 0 from 20 and we're left 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.

On to step 9:
When dividing 200 by 21, we get 9 with a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 7936.809
If we subtract 189 from 200, we 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.

Advancing to step 10:
When dividing 110 by 21, we get 5 with a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 7936.8095
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.

Moving on to step 11:
The number 21 fits into 50 2 times, leaving a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 7936.80952
If we subtract 42 from 50, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Let's proceed to step 12:
When dividing 80 by 21, we get 3 with a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 7936.809523
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.

Step 13:
21 goes into 170 8 times with a remainder of 2.
Put 8 as the next digit of the answer. 
Result so far: 7936.8095238
Deduct 168 from 170 and we're left 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.

Let's proceed to step 14:
If we divide 20 by 21, we get 0 and a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 7936.8095238
Subtract 0 from 20 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

The final outcome is 7936.8095238, with a leftover of 2e-08.