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A leap year check in three instructions

(hueffner.de)
420 points gnabgib | 6 comments | 15 May 25 21:57 UTC | HN request time: 1.182s | source | bottom
1. fuzunoglu ◴[16 May 25 01:42 UTC] No.44001081[source]▶
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.
replies(1): >>44001864 #
2. silisili ◴[16 May 25 04:34 UTC] No.44001864[source]▶
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).
replies(1): >>44001948 #
3. lkirkwood ◴[16 May 25 04:53 UTC] No.44001948[source]▶
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.
replies(2): >>44001961 #>>44002434 #
4. silisili ◴[16 May 25 04:55 UTC] No.44001961{3}[source]▶
Sure, but OP was talking about binary representation.
replies(1): >>44003353 #
5. Etheryte ◴[16 May 25 06:44 UTC] No.44002434{3}[source]▶
All odd numbers end in 1 in binary.
6. dmichulke ◴[16 May 25 09:25 UTC] No.44003353{4}[source]▶
GP's statement is true for all number systems with an even base (so also for binary and decimal)