84191609 ÷ 521 
The aim is to understand the frequency of 521 in 84191609.

Moving on to step 1:
If we divide 8 by 521, we get 0 and a remainder of 8.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 8 after subtracting 0 from 8.
Bring next digit (4) of the dividend behind the 8 and repeat the process: 84 / 521

Moving on to step 2:
84 divided by 521 is 0 with a remainder of 84.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtract 0 from 84 to get 84.
Grab the next digit (1) from the dividend, add it to 84, then carry on: 841 / 521

Advancing to step 3:
841 divided by 521 is 1 with a remainder of 320.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we take 521 away from 841, we end up with 320.
Fetch the next digit (9) from the dividend, attach it to 320 and continue: 3209 / 521

Step 4:
When dividing 3209 by 521, we get 6 with a remainder of 83.
The number 6 becomes the next digit in our result. 
Result so far: 16.0
Subtracting 3126 from 3209 leaves us with 83.
Take the next digit (1) from the dividend and append it to 83, then repeat: 831 / 521

On to step 5:
The number 521 fits into 831 1 times, leaving a remainder of 310.
The number 1 becomes the next digit in our result. 
Result so far: 161.0
The remainder is 310 after subtracting 521 from 831.
Fetch the next digit (6) from the dividend, attach it to 310 and continue: 3106 / 521

Going ahead to step 6:
3106 divided by 521 is 5 with a remainder of 501.
Use 5 as the next digit of our solution. 
Result so far: 1615.0
If we take 2605 away from 3106, we end up with 501.
Take the next digit (0) from the dividend and append it to 501, then repeat: 5010 / 521

Moving on to step 7:
When dividing 5010 by 521, we get 9 with a remainder of 321.
Put 9 as the next digit of the answer. 
Result so far: 16159.0
Deduct 4689 from 5010 and we're left with 321.
Fetch the next digit (9) from the dividend, attach it to 321 and continue: 3219 / 521

On to step 8:
3219 divided by 521 is 6 with a remainder of 93.
Record the quotient 6 as the next digit in the result. 
Result so far: 161596.0
Subtract 3126 from 3219 to get 93.
Since there are no more digits in the dividend, we add a zero to the remainder making it 930, and continue the process.

Step 9:
521 can be fit into 930 1 times, resulting in a remainder of 409.
Write down 1 as next digit of the result. 
Result so far: 161596.1
Deduct 521 from 930 and we're left with 409.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4090, and continue the process.

Going ahead to step 10:
The number 521 fits into 4090 7 times, leaving a remainder of 443.
Put 7 as the next digit of the answer. 
Result so far: 161596.17
The remainder is 443 after subtracting 3647 from 4090.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4430, and continue the process.

Let's proceed to step 11:
521 goes into 4430 8 times with a remainder of 262.
Record the quotient 8 as the next digit in the result. 
Result so far: 161596.178
If we take 4168 away from 4430, we end up with 262.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2620, and continue the process.

Moving on to step 12:
2620 divided by 521 is 5 with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 161596.1785
Subtract 2605 from 2620 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Step 13:
If we divide 150 by 521, we get 0 and a remainder of 150.
Write down 0 as next digit of the result. 
Result so far: 161596.1785
If we subtract 0 from 150, we get 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1500, and continue the process.

On to step 14:
521 can be fit into 1500 2 times, resulting in a remainder of 458.
Use 2 as the next digit of our solution. 
Result so far: 161596.178502
The remainder is 458 after subtracting 1042 from 1500.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4580, and continue the process.

Advancing to step 15:
When dividing 4580 by 521, we get 8 with a remainder of 412.
Use 8 as the next digit of our solution. 
Result so far: 161596.1785028
The remainder is 412 after subtracting 4168 from 4580.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4120, and continue the process.

Let's proceed to step 16:
521 can be fit into 4120 7 times, resulting in a remainder of 473.
Write down 7 as next digit of the result. 
Result so far: 161596.17850287
Subtract 3647 from 4120 to get 473.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4730, and continue the process.

The final result is 161596.17850287 with a remainder of 4.73e-07.