17871039 ÷ 561 
The aim is to understand the frequency of 561 in 17871039.

Let's proceed to step 1:
1 divided by 561 is 0 with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Include the next digit (7) from the dividend after 1, then repeat: 17 / 561

Let's proceed to step 2:
The number 561 fits into 17 0 times, leaving a remainder of 17.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 17 after subtracting 0 from 17.
Append the next digit (8) from the dividend to 17 and continue with: 178 / 561

Moving on to step 3:
If we divide 178 by 561, we get 0 and a remainder of 178.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 178 leaves us with 178.
Append the next digit (7) from the dividend to 178 and continue with: 1787 / 561

Step 4:
561 can be fit into 1787 3 times, resulting in a remainder of 104.
Use 3 as the next digit of our solution. 
Result so far: 3.0
If we take 1683 away from 1787, we end up with 104.
Bring next digit (1) of the dividend behind the 104 and repeat the process: 1041 / 561

Advancing to step 5:
561 can be fit into 1041 1 times, resulting in a remainder of 480.
Use 1 as the next digit of our solution. 
Result so far: 31.0
The remainder is 480 after subtracting 561 from 1041.
Bring next digit (0) of the dividend behind the 480 and repeat the process: 4800 / 561

On to step 6:
4800 divided by 561 is 8 with a remainder of 312.
The number 8 becomes the next digit in our result. 
Result so far: 318.0
Deduct 4488 from 4800 and we're left with 312.
Append the next digit (3) from the dividend to 312 and continue with: 3123 / 561

Step 7:
561 goes into 3123 5 times with a remainder of 318.
Write down 5 as next digit of the result. 
Result so far: 3185.0
If we take 2805 away from 3123, we end up with 318.
Append the next digit (9) from the dividend to 318 and continue with: 3189 / 561

Going ahead to step 8:
3189 divided by 561 is 5 with a remainder of 384.
Put 5 as the next digit of the answer. 
Result so far: 31855.0
Subtract 2805 from 3189 to get 384.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3840, and continue the process.

Moving on to step 9:
If we divide 3840 by 561, we get 6 and a remainder of 474.
Write down 6 as next digit of the result. 
Result so far: 31855.6
If we take 3366 away from 3840, we end up with 474.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4740, and continue the process.

Let's proceed to step 10:
561 can be fit into 4740 8 times, resulting in a remainder of 252.
The number 8 becomes the next digit in our result. 
Result so far: 31855.68
Subtract 4488 from 4740 to get 252.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2520, and continue the process.

Moving on to step 11:
When dividing 2520 by 561, we get 4 with a remainder of 276.
Write down 4 as next digit of the result. 
Result so far: 31855.684
The remainder is 276 after subtracting 2244 from 2520.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2760, and continue the process.

Advancing to step 12:
2760 divided by 561 is 4 with a remainder of 516.
Use 4 as the next digit of our solution. 
Result so far: 31855.6844
If we subtract 2244 from 2760, we get 516.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5160, and continue the process.

The final outcome is 31855.6844, with a leftover of 0.00516.