640915 divided by 21 
Let's see how many times 21 fits into 640915.

Moving on to step 1:
When dividing 6 by 21, we get 0 with a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Grab the next digit (4) from the dividend, add it to 6, then carry on: 64 / 21

Going ahead to step 2:
21 can be fit into 64 3 times, resulting in a remainder of 1.
Use 3 as the next digit of our solution. 
Result so far: 3.0
If we subtract 63 from 64, we get 1.
Take the next digit (0) from the dividend and append it to 1, then repeat: 10 / 21

Let's proceed to step 3:
10 divided by 21 is 0 with a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 30.0
Deduct 0 from 10 and we're left with 10.
Grab the next digit (9) from the dividend, add it to 10, then carry on: 109 / 21

Going ahead to step 4:
21 can be fit into 109 5 times, resulting in a remainder of 4.
Record the quotient 5 as the next digit in the result. 
Result so far: 305.0
Deduct 105 from 109 and we're left with 4.
Grab the next digit (1) from the dividend, add it to 4, then carry on: 41 / 21

Step 5:
The number 21 fits into 41 1 times, leaving a remainder of 20.
Write down 1 as next digit of the result. 
Result so far: 3051.0
The remainder is 20 after subtracting 21 from 41.
Bring next digit (5) of the dividend behind the 20 and repeat the process: 205 / 21

On to step 6:
205 divided by 21 is 9 with a remainder of 16.
Put 9 as the next digit of the answer. 
Result so far: 30519.0
If we subtract 189 from 205, we 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.

On to step 7:
When dividing 160 by 21, we get 7 with a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 30519.7
Deduct 147 from 160 and we're left 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.

Moving on to step 8:
If we divide 130 by 21, we get 6 and a remainder of 4.
Write down 6 as next digit of the result. 
Result so far: 30519.76
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 9:
21 can be fit into 40 1 times, resulting in a remainder of 19.
The next digit of our result is 1. 
Result so far: 30519.761
Subtracting 21 from 40 leaves us with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Going ahead to step 10:
21 can be fit into 190 9 times, resulting in a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 30519.7619
Subtracting 189 from 190 leaves us with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

On to step 11:
21 goes into 10 0 times with a remainder of 10.
Record the quotient 0 as the next digit in the result. 
Result so far: 30519.7619
If we subtract 0 from 10, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 12:
100 divided by 21 is 4 with a remainder of 16.
Use 4 as the next digit of our solution. 
Result so far: 30519.761904
If we take 84 away from 100, we end up 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.

Step 13:
When dividing 160 by 21, we get 7 with a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 30519.7619047
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.

Step 14:
When dividing 130 by 21, we get 6 with a remainder of 4.
Use 6 as the next digit of our solution. 
Result so far: 30519.76190476
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.

Our division results in 30519.76190476 with a remaining 4e-09.