We're dividing 15636251 by 861 
The aim is to understand the frequency of 861 in 15636251.

Advancing to step 1:
1 divided by 861 is 0 with a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 1 to get 1.
Grab the next digit (5) from the dividend, add it to 1, then carry on: 15 / 861

Going ahead to step 2:
If we divide 15 by 861, we get 0 and a remainder of 15.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 15 after subtracting 0 from 15.
Append the next digit (6) from the dividend to 15 and continue with: 156 / 861

Going ahead to step 3:
156 divided by 861 is 0 with a remainder of 156.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 156 to get 156.
Append the next digit (3) from the dividend to 156 and continue with: 1563 / 861

On to step 4:
1563 divided by 861 is 1 with a remainder of 702.
Use 1 as the next digit of our solution. 
Result so far: 1.0
If we subtract 861 from 1563, we get 702.
Take the next digit (6) from the dividend and append it to 702, then repeat: 7026 / 861

Step 5:
7026 divided by 861 is 8 with a remainder of 138.
Record the quotient 8 as the next digit in the result. 
Result so far: 18.0
Deduct 6888 from 7026 and we're left with 138.
Append the next digit (2) from the dividend to 138 and continue with: 1382 / 861

Going ahead to step 6:
If we divide 1382 by 861, we get 1 and a remainder of 521.
Record the quotient 1 as the next digit in the result. 
Result so far: 181.0
Deduct 861 from 1382 and we're left with 521.
Append the next digit (5) from the dividend to 521 and continue with: 5215 / 861

Moving on to step 7:
861 goes into 5215 6 times with a remainder of 49.
Write down 6 as next digit of the result. 
Result so far: 1816.0
Deduct 5166 from 5215 and we're left with 49.
Bring next digit (1) of the dividend behind the 49 and repeat the process: 491 / 861

Step 8:
861 goes into 491 0 times with a remainder of 491.
The next digit of our result is 0. 
Result so far: 18160.0
If we take 0 away from 491, we end up with 491.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4910, and continue the process.

Advancing to step 9:
861 goes into 4910 5 times with a remainder of 605.
The next digit of our result is 5. 
Result so far: 18160.5
The remainder is 605 after subtracting 4305 from 4910.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6050, and continue the process.

Let's proceed to step 10:
When dividing 6050 by 861, we get 7 with a remainder of 23.
Put 7 as the next digit of the answer. 
Result so far: 18160.57
If we subtract 6027 from 6050, we get 23.
Since there are no more digits in the dividend, we add a zero to the remainder making it 230, and continue the process.

Advancing to step 11:
If we divide 230 by 861, we get 0 and a remainder of 230.
Use 0 as the next digit of our solution. 
Result so far: 18160.57
Deduct 0 from 230 and we're left with 230.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2300, and continue the process.

Going ahead to step 12:
2300 divided by 861 is 2 with a remainder of 578.
The next digit of our result is 2. 
Result so far: 18160.5702
Deduct 1722 from 2300 and we're left with 578.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5780, and continue the process.

On to step 13:
5780 divided by 861 is 6 with a remainder of 614.
Write down 6 as next digit of the result. 
Result so far: 18160.57026
Deduct 5166 from 5780 and we're left with 614.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6140, and continue the process.

Advancing to step 14:
If we divide 6140 by 861, we get 7 and a remainder of 113.
Write down 7 as next digit of the result. 
Result so far: 18160.570267
The remainder is 113 after subtracting 6027 from 6140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1130, and continue the process.

On to step 15:
The number 861 fits into 1130 1 times, leaving a remainder of 269.
Use 1 as the next digit of our solution. 
Result so far: 18160.5702671
Subtract 861 from 1130 to get 269.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2690, and continue the process.

Step 16:
861 can be fit into 2690 3 times, resulting in a remainder of 107.
Write down 3 as next digit of the result. 
Result so far: 18160.57026713
Deduct 2583 from 2690 and we're left with 107.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1070, and continue the process.

The final result is 18160.57026713 with a remainder of 1.07e-07.