876 is divisible by 3. As an easy check for the divisibility by 3 for any number, simply add up the digits (8 + 7 + 6 for 876) and if the sum is a multiple of 3, then the number is divisible by 3.

No. 483 is not divisible by 6. A number is divisible by 6 if it is divisible by both 2 and 3. It is divisible by 2 if it is even and it is divisible by 3 if the sum of the digits is a multiple of 3. 483 is not divisible by 6 since it is not divisible by 2 although it is divisible by 3.