66191659 divided by 21 
Let's see how many times 21 fits into 66191659.

Step 1:
21 goes into 6 0 times with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Take the next digit (6) from the dividend and append it to 6, then repeat: 66 / 21

On to step 2:
66 divided by 21 is 3 with a remainder of 3.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Subtract 63 from 66 to get 3.
Grab the next digit (1) from the dividend, add it to 3, then carry on: 31 / 21

Let's proceed to step 3:
The number 21 fits into 31 1 times, leaving a remainder of 10.
The next digit of our result is 1. 
Result so far: 31.0
If we take 21 away from 31, we end up with 10.
Include the next digit (9) from the dividend after 10, then repeat: 109 / 21

Advancing to step 4:
If we divide 109 by 21, we get 5 and a remainder of 4.
Put 5 as the next digit of the answer. 
Result so far: 315.0
If we take 105 away from 109, we end up with 4.
Grab the next digit (1) from the dividend, add it to 4, then carry on: 41 / 21

Moving on to step 5:
21 goes into 41 1 times with a remainder of 20.
Use 1 as the next digit of our solution. 
Result so far: 3151.0
The remainder is 20 after subtracting 21 from 41.
Grab the next digit (6) from the dividend, add it to 20, then carry on: 206 / 21

Step 6:
The number 21 fits into 206 9 times, leaving a remainder of 17.
Use 9 as the next digit of our solution. 
Result so far: 31519.0
Subtracting 189 from 206 leaves us with 17.
Include the next digit (5) from the dividend after 17, then repeat: 175 / 21

Moving on to step 7:
The number 21 fits into 175 8 times, leaving a remainder of 7.
Record the quotient 8 as the next digit in the result. 
Result so far: 315198.0
Subtracting 168 from 175 leaves us with 7.
Grab the next digit (9) from the dividend, add it to 7, then carry on: 79 / 21

Step 8:
When dividing 79 by 21, we get 3 with a remainder of 16.
Write down 3 as next digit of the result. 
Result so far: 3151983.0
Subtract 63 from 79 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.

Step 9:
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: 3151983.7
Subtract 147 from 160 to 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.

Step 10:
When dividing 130 by 21, we get 6 with a remainder of 4.
The next digit of our result is 6. 
Result so far: 3151983.76
If we subtract 126 from 130, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Going ahead to step 11:
When dividing 40 by 21, we get 1 with a remainder of 19.
The next digit of our result is 1. 
Result so far: 3151983.761
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.

Going ahead to step 12:
21 can be fit into 190 9 times, resulting in a remainder of 1.
The next digit of our result is 9. 
Result so far: 3151983.7619
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.

Let's proceed to step 13:
21 can be fit into 10 0 times, resulting in a remainder of 10.
Put 0 as the next digit of the answer. 
Result so far: 3151983.7619
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.

On to step 14:
If we divide 100 by 21, we get 4 and a remainder of 16.
Write down 4 as next digit of the result. 
Result so far: 3151983.761904
Subtracting 84 from 100 leaves us 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 15:
21 can be fit into 160 7 times, resulting in a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 3151983.7619047
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 16:
The number 21 fits into 130 6 times, leaving a remainder of 4.
Use 6 as the next digit of our solution. 
Result so far: 3151983.76190476
If we take 126 away from 130, we end up 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.

After the division, we end up with 3151983.76190476 and a remainder of 4e-09.