An "even" number is divisible by 2 with no remainder. For integer N in integer base B:

If B is even:
One can determine if N is even or odd by looking at the least significant digit of N (B0). If it is odd then N is odd. If it is even, N is even.
If B is odd:
One can tell if N is even or odd by finding the sum of all the digits of N. If the sum is an even number then N is even. If the sum is odd, then N is odd.