odditudes-and-weirdities

Happy Semiprime Numbers Day! Semiprime numbers are the product of exactly 2 prime numbers , so 4 (2 X 2) and 6 (2 X 3) are semiprimes, but 8 (2 X 2 X 2) and 30 (2 X 3 X 5) are not. More examples are here: Public key cryptography depends on the difficulty of factoring very large semiprime numbers for its effectiveness. Semiprime Numbers Day is celebrated on the date 10/14, or October 14, since 10 and 14 are the largest consecutive semiprime numbers forming a valid date.

Happy Powerful Numbers Day! Powerful numbers  (aka squareful numbers) are ones such that for every number dividing it that is prime or 1, the square of the divisor is also a divisor. Powerful numbers are basically a subset of the composite numbers in addition to the number 1, and contain the square numbers as a subset. Here's some of the arithmetic that determines powerful numbers. We celebrate Powerful Numbers Day today because 9 and 27 are the largest powerful numbers that form a valid date: 9/27 or September 27.

Happy Square Numbers Day! Square numbers are the numbers formed when you square a positive integer, making them a fairly easy concept to grasp. Here is the beginning of the sequence: While triangular numbers are the integers representing the number of objects needed to form equilateral triangles, square numbers similarly form squares of different sizes. They are also a subset of the powerful numbers . We celebrate today as Square Numbers Day because the 2 largest consecutive square numbers that form a date are 9 and 16: 9/16 or September 16.

Happy World Goat Day! This is another holiday where the webpage I used to use for it disappeared so I'm writing one to replace it. As is often the case I don't know why today was selected for World Goat Day. As a species that was domesticated back in prehistoric times, today's date is unlikely to denote some milestone in human-goat relations. Regardless of why today's date is World Goat Day, goats have been important livestock for an estimated 10,000 years. But I don't think today is supposed to be about the domesticated goat in particular; since the original webpage I had for it was for a zoo, I suspect today is about celebrating all the animals in the goat genus . This includes guys like the Markhor (the world's largest goat), various ibexes like the Alpine Ibex , domesticated goats, et al. (Sorry Mountain Goat , but unfortunately you're not considered to be a true goat, though clearly a goat relative.) Further up the taxonomy hierarchy, goats are in the...

Happy Almost Perfect Numbers Day! Today we celebrate numbers that aren't perfect numbers but are almost perfect numbers  (aka slightly deficient numbers aka least defective numbers). Perfect numbers (in case you've forgotten) are the numbers such that if you sum up their divisors the result is 2 times the number itself. For example, the divisors of 6 are 1, 2, 3, and 6, and if you sum them up you get 1+2+3+6=12, which is also 2 x 6. Almost perfect numbers are numbers where the sum of the divisors is 1 less than 2 times the number. For example, the divisors of 4 are 1, 2, and 4, and the sum of them is 1+2+4 = 7, which is 1 less than 2 x 4. All the known almost perfect numbers are powers of 2, like 2x2 = 4, 2x2x2 = 8, 2x2x2x2 = 16, etc. It hasn't been proven that every almost perfect number is of this form, though given the computational power we have today, if other forms exist, they must be very large almost perfect numbers. Here is the beginning of the almost perfect numb...

Happy Geek Pride Day! Today is also one of the geekiest days of the year, with holidays relating to Star Wars, The Hitchhiker's Guide to the Galaxy, and the Discworld books: Two weeks after the death in 2001 of Douglas Adams, author of The Hitchhiker's Guide to the Galaxy and related books, is celebrated as Towel Day . (Towels were considered important and versatile items essential for hitchhiking the galaxy.) The original Star Wars movie was released on this date in 1977, inspiring Star Wars Day . In Terry Pratchett's Discworld books, a climactic revolution took place on this date that is remembered as both the Glorious Twenty-fifth of May and as Wear the Lilac Day . And Geek Pride Day is basically an umbrella holiday for these individual geeky holidays.

On this date in 1930 the Star Wars character Yoda was introduced to American audiences in the film The Empire Strikes Back . Or as he'd probably say "Introduced to American audiences, Yoda was". An interesting way of talking, Yoda had. Understandable he was. Disordered though, the sentence structure was. More here there is. And a translator here is. Celebrate by watching/reading Star Wars material, you should. By Muboshgu - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=114758211