We look at the division of 16920668 by 644 
The aim is to understand the frequency of 644 in 16920668.

Step 1:
If we divide 1 by 644, we get 0 and a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 1 after subtracting 0 from 1.
Fetch the next digit (6) from the dividend, attach it to 1 and continue: 16 / 644

Step 2:
The number 644 fits into 16 0 times, leaving a remainder of 16.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 16, we end up with 16.
Bring next digit (9) of the dividend behind the 16 and repeat the process: 169 / 644

On to step 3:
644 goes into 169 0 times with a remainder of 169.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 169 leaves us with 169.
Append the next digit (2) from the dividend to 169 and continue with: 1692 / 644

Advancing to step 4:
644 goes into 1692 2 times with a remainder of 404.
Put 2 as the next digit of the answer. 
Result so far: 2.0
If we take 1288 away from 1692, we end up with 404.
Include the next digit (0) from the dividend after 404, then repeat: 4040 / 644

On to step 5:
If we divide 4040 by 644, we get 6 and a remainder of 176.
The next digit of our result is 6. 
Result so far: 26.0
The remainder is 176 after subtracting 3864 from 4040.
Grab the next digit (6) from the dividend, add it to 176, then carry on: 1766 / 644

Going ahead to step 6:
644 can be fit into 1766 2 times, resulting in a remainder of 478.
Record the quotient 2 as the next digit in the result. 
Result so far: 262.0
Deduct 1288 from 1766 and we're left with 478.
Fetch the next digit (6) from the dividend, attach it to 478 and continue: 4786 / 644

Moving on to step 7:
The number 644 fits into 4786 7 times, leaving a remainder of 278.
The number 7 becomes the next digit in our result. 
Result so far: 2627.0
The remainder is 278 after subtracting 4508 from 4786.
Append the next digit (8) from the dividend to 278 and continue with: 2788 / 644

Step 8:
When dividing 2788 by 644, we get 4 with a remainder of 212.
Write down 4 as next digit of the result. 
Result so far: 26274.0
Deduct 2576 from 2788 and we're left with 212.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2120, and continue the process.

Step 9:
644 goes into 2120 3 times with a remainder of 188.
Record the quotient 3 as the next digit in the result. 
Result so far: 26274.3
If we take 1932 away from 2120, we end up with 188.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1880, and continue the process.

Moving on to step 10:
1880 divided by 644 is 2 with a remainder of 592.
Put 2 as the next digit of the answer. 
Result so far: 26274.32
Deduct 1288 from 1880 and we're left with 592.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5920, and continue the process.

Let's proceed to step 11:
When dividing 5920 by 644, we get 9 with a remainder of 124.
The next digit of our result is 9. 
Result so far: 26274.329
If we take 5796 away from 5920, we end up with 124.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1240, and continue the process.

Advancing to step 12:
1240 divided by 644 is 1 with a remainder of 596.
The number 1 becomes the next digit in our result. 
Result so far: 26274.3291
Deduct 644 from 1240 and we're left with 596.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5960, and continue the process.

On to step 13:
5960 divided by 644 is 9 with a remainder of 164.
Write down 9 as next digit of the result. 
Result so far: 26274.32919
The remainder is 164 after subtracting 5796 from 5960.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1640, and continue the process.

Going ahead to step 14:
1640 divided by 644 is 2 with a remainder of 352.
The number 2 becomes the next digit in our result. 
Result so far: 26274.329192
If we take 1288 away from 1640, we end up with 352.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3520, and continue the process.

Advancing to step 15:
The number 644 fits into 3520 5 times, leaving a remainder of 300.
Put 5 as the next digit of the answer. 
Result so far: 26274.3291925
Deduct 3220 from 3520 and we're left with 300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3000, and continue the process.

Step 16:
644 can be fit into 3000 4 times, resulting in a remainder of 424.
Write down 4 as next digit of the result. 
Result so far: 26274.32919254
Deduct 2576 from 3000 and we're left with 424.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4240, and continue the process.

The quotient of the division is 26274.32919254, and the remainder is 4.24e-07.