Taking a look at numbers in binary reveals some interesting patterns. Although seems obvious, it was interesting to me when I realized that all prime numbers except 2 end with 1.
Not trying to be a jerk, but why is that interesting? Am I missing something more than all odd numbers end in 1, and primes by their nature cannot be even(except 2, as you mentioned).
Just nitpick but all odd numbers end in an odd number, not 1, and all even numbers end in an even number i.e. a multiple of 2.