Without going into why I was doing so, today I had the "opportunity" to answer the question, "What is the square root of 523,457?" And I learned some mathematical truths by trying to answer this question.

I began be trying to factor it down to prime numbers -- but that left me with 11 x 23 x 2069. Then I tried factoring down an approximation of the original number, in this case, 523,456 = 8 x 8 x 8179. 8,179 is a prime number.

I finally came at it from the answer instead of the question, homing in on the answer I needed. The quick version is as follows, with the square root of 523,457 represented as x:

700 < x < 800

720 < x < 730

723 < x < 724

Anyway, the point of going on about this isn't to figure out the square root of this odd number, but to share something I discovered (for myself, not for the mathematical world at large, which surely has already figured this out). The original number, 523,457, is obviously not a perfect square because perfect squares never end in 7. I'd never realized the ban on sevens before, but it makes sense when you consider how you multiply multi-digit numbers.

Looking into this further, I realized that perfect squares always have to end in 0, 1, 4, 5, 6, or 9. I discovered this by squaring each of the first 10 numbers.

But I also discovered a pattern that I hadn't noticed before. Looking just at the last digit, if you start to list the perfect squares in order, those final digits follow the pattern 0, 1, 4, 9, 6, 5, 6, 9, 4, 1, 0, ... I find not only the existence of the pattern intriguing, but also the fact that it's a symmetrical pattern with an intervening zero.

There's also a pattern to the rest of the perfect squares. If you drop the final digit of each perfect square, there is a stepwise addition pattern that shifts up whenever you reach a perfect square that ends with a 9. You'll have to look at it yourelf, but basically, you start at 0. When you hit 9, you start adding 1 to get each of the next perfect squares. When you hit the next perfect square that ends in 9 (49), then you start adding 2 to get the first digit of each number.

I know, most people will just think "so what?" But for me, I get a great feeling from discovering a truth for myself. I also love logic puzzles, and this is something of that sort. Now that I've figured this out, I'll have to try to find the underlying logic of the decimal system that makes this so. And I'll have to see if there is a similar pattern for perfect cubes.