## Thursday, February 2, 2017

### Primal entertainment

Really, totally primal. ๐

Ron Rivest talking about RSA-129 (a product of two prime numbers that was set as a factoring challenge in 1977) and its factorization in 1994 using the internet:

RSA-129 = 114381625 7578888676 6923577997 6146612010 2182967212 4236256256 1842935706 9352457338 9783059712 3563958705 0589890751 4759929002 6879543541
=
3490 5295108476 5094914784 9619903898 1334177646 3849338784 3990820577
$\times$
32769 1329932667 0954996198 8190834461 4131776429 6799294253 9798288533.

Inspired by that video, here are a couple of fun numbers, for numbers geeks:

๐ 70,000,000,000,000,000,000,003 is a prime number. It's an interesting prime number, because the number of zeros in the middle (21) is the product of the 7 and the 3, both of which are, of course, prime numbers themselves. This makes the number very easy to memorize and surprise your friends with. If you want to confuse them, just say it like this: "seventy sextillion and three."

๐ 99,999,999,999,999,999,999,977 is also a prime number, the largest prime number under a googol ($10^{100}$) that has the form  $p = 10^{n} - n$, with $n = 23$, meaning that if you add 23 to this number you get $10^{23}$ or a 1 followed by 23 zeros. Here's how you say this number: "ninety-nine sextillion, nine hundred ninety-nine quintillion, nine hundred ninety-nine quadrillion, nine hundred ninety-nine trillion, nine hundred ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, and nine hundred seventy-seven." Hilarious at parties.