21478218 divided by 408 
The aim is to understand the frequency of 408 in 21478218.

Let's proceed to step 1:
The number 408 fits into 2 0 times, leaving a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 408

Going ahead to step 2:
21 divided by 408 is 0 with a remainder of 21.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 21 after subtracting 0 from 21.
Include the next digit (4) from the dividend after 21, then repeat: 214 / 408

On to step 3:
408 goes into 214 0 times with a remainder of 214.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 214 after subtracting 0 from 214.
Fetch the next digit (7) from the dividend, attach it to 214 and continue: 2147 / 408

Advancing to step 4:
If we divide 2147 by 408, we get 5 and a remainder of 107.
The number 5 becomes the next digit in our result. 
Result so far: 5.0
If we subtract 2040 from 2147, we get 107.
Take the next digit (8) from the dividend and append it to 107, then repeat: 1078 / 408

Going ahead to step 5:
408 goes into 1078 2 times with a remainder of 262.
Use 2 as the next digit of our solution. 
Result so far: 52.0
If we subtract 816 from 1078, we get 262.
Include the next digit (2) from the dividend after 262, then repeat: 2622 / 408

Going ahead to step 6:
When dividing 2622 by 408, we get 6 with a remainder of 174.
Use 6 as the next digit of our solution. 
Result so far: 526.0
Subtract 2448 from 2622 to get 174.
Append the next digit (1) from the dividend to 174 and continue with: 1741 / 408

Moving on to step 7:
If we divide 1741 by 408, we get 4 and a remainder of 109.
Put 4 as the next digit of the answer. 
Result so far: 5264.0
If we subtract 1632 from 1741, we get 109.
Fetch the next digit (8) from the dividend, attach it to 109 and continue: 1098 / 408

Going ahead to step 8:
408 can be fit into 1098 2 times, resulting in a remainder of 282.
Use 2 as the next digit of our solution. 
Result so far: 52642.0
If we take 816 away from 1098, we end up with 282.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2820, and continue the process.

On to step 9:
408 can be fit into 2820 6 times, resulting in a remainder of 372.
Record the quotient 6 as the next digit in the result. 
Result so far: 52642.6
If we take 2448 away from 2820, we end up with 372.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3720, and continue the process.

Advancing to step 10:
When dividing 3720 by 408, we get 9 with a remainder of 48.
Write down 9 as next digit of the result. 
Result so far: 52642.69
The remainder is 48 after subtracting 3672 from 3720.
Since there are no more digits in the dividend, we add a zero to the remainder making it 480, and continue the process.

On to step 11:
When dividing 480 by 408, we get 1 with a remainder of 72.
Record the quotient 1 as the next digit in the result. 
Result so far: 52642.691
Subtracting 408 from 480 leaves us with 72.
Since there are no more digits in the dividend, we add a zero to the remainder making it 720, and continue the process.

Advancing to step 12:
When dividing 720 by 408, we get 1 with a remainder of 312.
Write down 1 as next digit of the result. 
Result so far: 52642.6911
Subtracting 408 from 720 leaves us with 312.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3120, and continue the process.

The final outcome is 52642.6911, with a leftover of 0.00312.