51391305 divided by 661 
The aim is to understand the frequency of 661 in 51391305.

On to step 1:
The number 661 fits into 5 0 times, leaving a remainder of 5.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 5 after subtracting 0 from 5.
Grab the next digit (1) from the dividend, add it to 5, then carry on: 51 / 661

Going ahead to step 2:
51 divided by 661 is 0 with a remainder of 51.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 51 leaves us with 51.
Include the next digit (3) from the dividend after 51, then repeat: 513 / 661

Let's proceed to step 3:
If we divide 513 by 661, we get 0 and a remainder of 513.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 513 to get 513.
Take the next digit (9) from the dividend and append it to 513, then repeat: 5139 / 661

Advancing to step 4:
If we divide 5139 by 661, we get 7 and a remainder of 512.
Put 7 as the next digit of the answer. 
Result so far: 7.0
If we subtract 4627 from 5139, we get 512.
Bring next digit (1) of the dividend behind the 512 and repeat the process: 5121 / 661

Moving on to step 5:
661 goes into 5121 7 times with a remainder of 494.
The number 7 becomes the next digit in our result. 
Result so far: 77.0
Subtracting 4627 from 5121 leaves us with 494.
Grab the next digit (3) from the dividend, add it to 494, then carry on: 4943 / 661

Let's proceed to step 6:
661 goes into 4943 7 times with a remainder of 316.
The number 7 becomes the next digit in our result. 
Result so far: 777.0
If we take 4627 away from 4943, we end up with 316.
Fetch the next digit (0) from the dividend, attach it to 316 and continue: 3160 / 661

Let's proceed to step 7:
661 goes into 3160 4 times with a remainder of 516.
Write down 4 as next digit of the result. 
Result so far: 7774.0
Deduct 2644 from 3160 and we're left with 516.
Grab the next digit (5) from the dividend, add it to 516, then carry on: 5165 / 661

Going ahead to step 8:
661 goes into 5165 7 times with a remainder of 538.
The next digit of our result is 7. 
Result so far: 77747.0
Subtracting 4627 from 5165 leaves us with 538.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5380, and continue the process.

Moving on to step 9:
When dividing 5380 by 661, we get 8 with a remainder of 92.
Record the quotient 8 as the next digit in the result. 
Result so far: 77747.8
Subtract 5288 from 5380 to get 92.
Since there are no more digits in the dividend, we add a zero to the remainder making it 920, and continue the process.

Going ahead to step 10:
661 goes into 920 1 times with a remainder of 259.
Put 1 as the next digit of the answer. 
Result so far: 77747.81
The remainder is 259 after subtracting 661 from 920.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2590, and continue the process.

Step 11:
When dividing 2590 by 661, we get 3 with a remainder of 607.
The number 3 becomes the next digit in our result. 
Result so far: 77747.813
If we take 1983 away from 2590, we end up with 607.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6070, and continue the process.

Going ahead to step 12:
661 goes into 6070 9 times with a remainder of 121.
Put 9 as the next digit of the answer. 
Result so far: 77747.8139
If we take 5949 away from 6070, we end up with 121.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1210, and continue the process.

Going ahead to step 13:
The number 661 fits into 1210 1 times, leaving a remainder of 549.
The next digit of our result is 1. 
Result so far: 77747.81391
Subtract 661 from 1210 to get 549.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5490, and continue the process.

Moving on to step 14:
5490 divided by 661 is 8 with a remainder of 202.
Write down 8 as next digit of the result. 
Result so far: 77747.813918
If we take 5288 away from 5490, we end up with 202.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2020, and continue the process.

Going ahead to step 15:
When dividing 2020 by 661, we get 3 with a remainder of 37.
Use 3 as the next digit of our solution. 
Result so far: 77747.8139183
Deduct 1983 from 2020 and we're left with 37.
Since there are no more digits in the dividend, we add a zero to the remainder making it 370, and continue the process.

Going ahead to step 16:
If we divide 370 by 661, we get 0 and a remainder of 370.
Put 0 as the next digit of the answer. 
Result so far: 77747.8139183
Subtract 0 from 370 to get 370.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3700, and continue the process.

The final outcome is 77747.8139183, with a leftover of 3.7e-07.