We look at the division of 594936 by 21 
The aim is to understand the frequency of 21 in 594936.

Advancing to step 1:
21 can be fit into 5 0 times, resulting in a remainder of 5.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 5 leaves us with 5.
Append the next digit (9) from the dividend to 5 and continue with: 59 / 21

Let's proceed to step 2:
The number 21 fits into 59 2 times, leaving a remainder of 17.
Use 2 as the next digit of our solution. 
Result so far: 2.0
The remainder is 17 after subtracting 42 from 59.
Bring next digit (4) of the dividend behind the 17 and repeat the process: 174 / 21

Moving on to step 3:
174 divided by 21 is 8 with a remainder of 6.
Record the quotient 8 as the next digit in the result. 
Result so far: 28.0
Deduct 168 from 174 and we're left with 6.
Bring next digit (9) of the dividend behind the 6 and repeat the process: 69 / 21

Advancing to step 4:
If we divide 69 by 21, we get 3 and a remainder of 6.
Record the quotient 3 as the next digit in the result. 
Result so far: 283.0
If we take 63 away from 69, we end up with 6.
Take the next digit (3) from the dividend and append it to 6, then repeat: 63 / 21

On to step 5:
If we divide 63 by 21, we get 3 and a remainder of 0.
Put 3 as the next digit of the answer. 
Result so far: 2833.0
Subtracting 63 from 63 leaves us with 0.
Bring next digit (6) of the dividend behind the 0 and repeat the process: 6 / 21

On to step 6:
If we divide 6 by 21, we get 0 and a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 28330.0
Deduct 0 from 6 and we're left with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 7:
When dividing 60 by 21, we get 2 with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 28330.2
Deduct 42 from 60 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Let's proceed to step 8:
180 divided by 21 is 8 with a remainder of 12.
Use 8 as the next digit of our solution. 
Result so far: 28330.28
If we take 168 away from 180, we end up with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Advancing to step 9:
21 can be fit into 120 5 times, resulting in a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 28330.285
Deduct 105 from 120 and we're left with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 10:
21 goes into 150 7 times with a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 28330.2857
If we take 147 away from 150, we end up with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Step 11:
When dividing 30 by 21, we get 1 with a remainder of 9.
The next digit of our result is 1. 
Result so far: 28330.28571
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 12:
90 divided by 21 is 4 with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 28330.285714
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 13:
If we divide 60 by 21, we get 2 and a remainder of 18.
Record the quotient 2 as the next digit in the result. 
Result so far: 28330.2857142
The remainder is 18 after subtracting 42 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

On to step 14:
When dividing 180 by 21, we get 8 with a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 28330.28571428
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The quotient of the division is 28330.28571428, and the remainder is 1.2e-08.