We look at the division of 91553359 by 621 
The aim is to understand the frequency of 621 in 91553359.

Going ahead to step 1:
621 goes into 9 0 times with a remainder of 9.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 9, we get 9.
Fetch the next digit (1) from the dividend, attach it to 9 and continue: 91 / 621

Advancing to step 2:
The number 621 fits into 91 0 times, leaving a remainder of 91.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtract 0 from 91 to get 91.
Bring next digit (5) of the dividend behind the 91 and repeat the process: 915 / 621

Moving on to step 3:
The number 621 fits into 915 1 times, leaving a remainder of 294.
The next digit of our result is 1. 
Result so far: 1.0
If we take 621 away from 915, we end up with 294.
Include the next digit (5) from the dividend after 294, then repeat: 2945 / 621

Moving on to step 4:
The number 621 fits into 2945 4 times, leaving a remainder of 461.
Put 4 as the next digit of the answer. 
Result so far: 14.0
Subtracting 2484 from 2945 leaves us with 461.
Append the next digit (3) from the dividend to 461 and continue with: 4613 / 621

Advancing to step 5:
621 goes into 4613 7 times with a remainder of 266.
The number 7 becomes the next digit in our result. 
Result so far: 147.0
Subtract 4347 from 4613 to get 266.
Take the next digit (3) from the dividend and append it to 266, then repeat: 2663 / 621

Let's proceed to step 6:
621 can be fit into 2663 4 times, resulting in a remainder of 179.
Use 4 as the next digit of our solution. 
Result so far: 1474.0
Subtract 2484 from 2663 to get 179.
Include the next digit (5) from the dividend after 179, then repeat: 1795 / 621

Going ahead to step 7:
The number 621 fits into 1795 2 times, leaving a remainder of 553.
The number 2 becomes the next digit in our result. 
Result so far: 14742.0
If we take 1242 away from 1795, we end up with 553.
Append the next digit (9) from the dividend to 553 and continue with: 5539 / 621

On to step 8:
621 goes into 5539 8 times with a remainder of 571.
Put 8 as the next digit of the answer. 
Result so far: 147428.0
The remainder is 571 after subtracting 4968 from 5539.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5710, and continue the process.

Advancing to step 9:
The number 621 fits into 5710 9 times, leaving a remainder of 121.
Put 9 as the next digit of the answer. 
Result so far: 147428.9
The remainder is 121 after subtracting 5589 from 5710.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1210, and continue the process.

On to step 10:
621 can be fit into 1210 1 times, resulting in a remainder of 589.
The next digit of our result is 1. 
Result so far: 147428.91
The remainder is 589 after subtracting 621 from 1210.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5890, and continue the process.

Moving on to step 11:
621 goes into 5890 9 times with a remainder of 301.
The number 9 becomes the next digit in our result. 
Result so far: 147428.919
The remainder is 301 after subtracting 5589 from 5890.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3010, and continue the process.

Moving on to step 12:
If we divide 3010 by 621, we get 4 and a remainder of 526.
The next digit of our result is 4. 
Result so far: 147428.9194
Deduct 2484 from 3010 and we're left with 526.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5260, and continue the process.

Advancing to step 13:
5260 divided by 621 is 8 with a remainder of 292.
Use 8 as the next digit of our solution. 
Result so far: 147428.91948
If we subtract 4968 from 5260, we get 292.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2920, and continue the process.

Going ahead to step 14:
2920 divided by 621 is 4 with a remainder of 436.
The next digit of our result is 4. 
Result so far: 147428.919484
If we subtract 2484 from 2920, we get 436.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4360, and continue the process.

Moving on to step 15:
4360 divided by 621 is 7 with a remainder of 13.
The next digit of our result is 7. 
Result so far: 147428.9194847
Subtracting 4347 from 4360 leaves us with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 16:
621 goes into 130 0 times with a remainder of 130.
Record the quotient 0 as the next digit in the result. 
Result so far: 147428.9194847
If we subtract 0 from 130, we get 130.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1300, and continue the process.

The quotient of the division is 147428.9194847, and the remainder is 1.3e-07.