21490 ÷ 6 = 3581 R4
Alright, let's work through the division of 21490 by 6 step by step.

Step 1:
6 goes into 2 0 times with a remainder of 2.
Write down 0 as next digit of of the result. 
Result so far: 0
Subtract 0 from 2 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 6

Step 2:
6 goes into 21 3 times with a remainder of 3.
Write down 3 as next digit of of the result. 
Result so far: 3
Subtract 18 from 21 to get 3.
Bring next digit (4) of the dividend behind the 3 and repeat the process: 34 / 6

Step 3:
6 goes into 34 5 times with a remainder of 4.
Write down 5 as next digit of of the result. 
Result so far: 35
Subtract 30 from 34 to get 4.
Bring next digit (9) of the dividend behind the 4 and repeat the process: 49 / 6

Step 4:
6 goes into 49 8 times with a remainder of 1.
Write down 8 as next digit of of the result. 
Result so far: 358
Subtract 48 from 49 to get 1.
Bring next digit (0) of the dividend behind the 1 and repeat the process: 10 / 6

Step 5:
6 goes into 10 1 times with a remainder of 4.
Write down 1 as next digit of of the result. 
Result so far: 3581
Subtract 6 from 10 to get 4.

The final result is 3581 with a remainder of 4.