745889 divided by 21 
The aim is to understand the frequency of 21 in 745889.

Moving on to step 1:
If we divide 7 by 21, we get 0 and a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Take the next digit (4) from the dividend and append it to 7, then repeat: 74 / 21

Moving on to step 2:
21 goes into 74 3 times with a remainder of 11.
Write down 3 as next digit of the result. 
Result so far: 3.0
If we subtract 63 from 74, we get 11.
Fetch the next digit (5) from the dividend, attach it to 11 and continue: 115 / 21

Advancing to step 3:
When dividing 115 by 21, we get 5 with a remainder of 10.
Record the quotient 5 as the next digit in the result. 
Result so far: 35.0
The remainder is 10 after subtracting 105 from 115.
Bring next digit (8) of the dividend behind the 10 and repeat the process: 108 / 21

Going ahead to step 4:
The number 21 fits into 108 5 times, leaving a remainder of 3.
Put 5 as the next digit of the answer. 
Result so far: 355.0
If we subtract 105 from 108, we get 3.
Take the next digit (8) from the dividend and append it to 3, then repeat: 38 / 21

Going ahead to step 5:
21 goes into 38 1 times with a remainder of 17.
Record the quotient 1 as the next digit in the result. 
Result so far: 3551.0
Subtract 21 from 38 to get 17.
Take the next digit (9) from the dividend and append it to 17, then repeat: 179 / 21

Advancing to step 6:
21 can be fit into 179 8 times, resulting in a remainder of 11.
The next digit of our result is 8. 
Result so far: 35518.0
Subtracting 168 from 179 leaves us 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:
110 divided by 21 is 5 with a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 35518.5
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.

Going ahead to step 8:
21 can be fit into 50 2 times, resulting in a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 35518.52
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 9:
21 goes into 80 3 times with a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 35518.523
Subtract 63 from 80 to 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 10:
When dividing 170 by 21, we get 8 with a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 35518.5238
The remainder is 2 after subtracting 168 from 170.
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 11:
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: 35518.5238
Subtracting 0 from 20 leaves us 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.

Moving on to step 12:
200 divided by 21 is 9 with a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 35518.523809
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.

Advancing to step 13:
21 goes into 110 5 times with a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 35518.5238095
If we take 105 away from 110, we end up 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.

Going ahead to step 14:
The number 21 fits into 50 2 times, leaving a remainder of 8.
The next digit of our result is 2. 
Result so far: 35518.52380952
The remainder is 8 after subtracting 42 from 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

After the division, we end up with 35518.52380952 and a remainder of 8e-09.