6679

This number is a prime.

6679 ≡ 1 (mod 6), 6679 ≡ 1 (mod 6), 6679 ≡ 1 (mod 7), 6679 ≡ 1 (mod 9). [Liu]

The divisibility rule of 6679 of what times the last digit added to the rest of the number if it is divisible by 6679 is also a prime number. [Pennington]