We divide 85663857 by 521
The aim is to understand the frequency of 521 in 85663857.

Moving on to step 1:
8 divided by 521 is 0 with a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 8 after subtracting 0 from 8.
Take the next digit (5) from the dividend and append it to 8, then repeat: 85 / 521

Step 2:
85 divided by 521 is 0 with a remainder of 85.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 85 and we're left with 85.
Fetch the next digit (6) from the dividend, attach it to 85 and continue: 856 / 521

Advancing to step 3:
The number 521 fits into 856 1 times, leaving a remainder of 335.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we subtract 521 from 856, we get 335.
Include the next digit (6) from the dividend after 335, then repeat: 3356 / 521

Let's proceed to step 4:
3356 divided by 521 is 6 with a remainder of 230.
Write down 6 as next digit of the result. 
Result so far: 16.0
If we take 3126 away from 3356, we end up with 230.
Append the next digit (3) from the dividend to 230 and continue with: 2303 / 521

Step 5:
521 goes into 2303 4 times with a remainder of 219.
Put 4 as the next digit of the answer. 
Result so far: 164.0
If we take 2084 away from 2303, we end up with 219.
Append the next digit (8) from the dividend to 219 and continue with: 2198 / 521

Step 6:
2198 divided by 521 is 4 with a remainder of 114.
The number 4 becomes the next digit in our result. 
Result so far: 1644.0
Subtract 2084 from 2198 to get 114.
Fetch the next digit (5) from the dividend, attach it to 114 and continue: 1145 / 521

Let's proceed to step 7:
If we divide 1145 by 521, we get 2 and a remainder of 103.
Put 2 as the next digit of the answer. 
Result so far: 16442.0
The remainder is 103 after subtracting 1042 from 1145.
Fetch the next digit (7) from the dividend, attach it to 103 and continue: 1037 / 521

Step 8:
If we divide 1037 by 521, we get 1 and a remainder of 516.
The number 1 becomes the next digit in our result. 
Result so far: 164421.0
Subtracting 521 from 1037 leaves us with 516.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5160, and continue the process.

Let's proceed to step 9:
5160 divided by 521 is 9 with a remainder of 471.
Write down 9 as next digit of the result. 
Result so far: 164421.9
The remainder is 471 after subtracting 4689 from 5160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4710, and continue the process.

Going ahead to step 10:
The number 521 fits into 4710 9 times, leaving a remainder of 21.
Use 9 as the next digit of our solution. 
Result so far: 164421.99
The remainder is 21 after subtracting 4689 from 4710.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

The final result is 164421.99 with a remainder of 0.021.