901225 divided by 21 
We're looking to find how many times 21 goes into 901225.

Advancing to step 1:
9 divided by 21 is 0 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.
Include the next digit (0) from the dividend after 9, then repeat: 90 / 21

Step 2:
90 divided by 21 is 4 with a remainder of 6.
Record the quotient 4 as the next digit in the result. 
Result so far: 4.0
Deduct 84 from 90 and we're left with 6.
Append the next digit (1) from the dividend to 6 and continue with: 61 / 21

Step 3:
If we divide 61 by 21, we get 2 and a remainder of 19.
Put 2 as the next digit of the answer. 
Result so far: 42.0
The remainder is 19 after subtracting 42 from 61.
Append the next digit (2) from the dividend to 19 and continue with: 192 / 21

On to step 4:
If we divide 192 by 21, we get 9 and a remainder of 3.
Use 9 as the next digit of our solution. 
Result so far: 429.0
The remainder is 3 after subtracting 189 from 192.
Bring next digit (2) of the dividend behind the 3 and repeat the process: 32 / 21

Advancing to step 5:
32 divided by 21 is 1 with a remainder of 11.
Record the quotient 1 as the next digit in the result. 
Result so far: 4291.0
The remainder is 11 after subtracting 21 from 32.
Include the next digit (5) from the dividend after 11, then repeat: 115 / 21

Advancing to step 6:
The number 21 fits into 115 5 times, leaving a remainder of 10.
Write down 5 as next digit of the result. 
Result so far: 42915.0
Deduct 105 from 115 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Moving on to step 7:
The number 21 fits into 100 4 times, leaving a remainder of 16.
The next digit of our result is 4. 
Result so far: 42915.4
Deduct 84 from 100 and we're left with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Advancing to step 8:
21 goes into 160 7 times with a remainder of 13.
Write down 7 as next digit of the result. 
Result so far: 42915.47
If we subtract 147 from 160, we get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Advancing to step 9:
130 divided by 21 is 6 with a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 42915.476
Deduct 126 from 130 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 10:
When dividing 40 by 21, we get 1 with a remainder of 19.
Put 1 as the next digit of the answer. 
Result so far: 42915.4761
If we subtract 21 from 40, we get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Moving on to step 11:
190 divided by 21 is 9 with a remainder of 1.
The number 9 becomes the next digit in our result. 
Result so far: 42915.47619
Subtract 189 from 190 to get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Moving on to step 12:
If we divide 10 by 21, we get 0 and a remainder of 10.
The next digit of our result is 0. 
Result so far: 42915.47619
Subtracting 0 from 10 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Going ahead to step 13:
The number 21 fits into 100 4 times, leaving a remainder of 16.
The number 4 becomes the next digit in our result. 
Result so far: 42915.4761904
Subtract 84 from 100 to get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Advancing to step 14:
160 divided by 21 is 7 with a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 42915.47619047
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Our division results in 42915.47619047 with a remaining 1.3e-08.