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New Largest Known Prime Number Has More Than 23 Million Digits

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Prime numbers come in all sizes: They go down to single digits and grow infinitely larger. But calculating the exact quantity of the largest prime numbers in existence takes serious time and effort. Now, thanks to help from a volunteer and his computer, the Great Internet Mersenne Prime Search (GIMPS) has identified the newest largest prime number we know of.

The prime number has 23,249,425 digits, surpassing the previous record holder by 1 million digits. It can be written as 277,232,917-1 or M77232917. Like other prime numbers, the quantity can only be divided by one and itself. But unlike some smaller primes, this one joins a special category called Mersenne primes.

Mersenne primes are found by calculating numbers to the second power and subtracting the value of one from the total. Only 50 prime numbers have been found this way, and a lot of computing power is required to uncover them.

Since 1996, GIMPS has been crowdsourcing computers to discover larger and larger prime numbers. Anyone can download their program and dedicate their unused processing power to churning out algorithms in search of the next record breaker. Volunteers whose computers successfully identify a new prime number are eligible for a cash reward of up to $3000.

The most recent winner was Jonathon Pace, a 51-year-old electrical engineer from Tennessee. His computer calculated the number M77232917 on December 26, and its prime status was independently verified by four separate computers.

GIMPS is constantly outdoing itself, with the previous largest prime announced just two years ago. If you'd like to join the effort, their prime-hunting software is free to download. But don't expect instant results: Pace was volunteering with GIMPS for 14 years before his altruism paid off. 

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Australian University Evacuated After Rotten Durian Smell Mistaken for Gas Leak
Mohd Rasfan, AFP/Getty Images
Mohd Rasfan, AFP/Getty Images

If you’ve ever been within sniffing distance of a durian, you would know it: The odor of the Southeast Asian fruit has been compared to decaying flesh, old garbage, and rotten eggs. The scent is so pungent that it prompted the recent evacuation of a university library in Melbourne, Australia, the Australian Associated Press reports.

Firefighters were called to investigate the scene on Saturday, April 28 after a strong smell was reported in the university library of the Royal Melbourne Institute of Technology. Police initially suspected it was a gas leak coming from the potentially harmful chemicals stored at the site. It was only after about 600 students and faculty members were evacuated that firefighters wearing gas masks discovered the true source of the stench: a durian that had been left to rot in a cupboard.

Putrid gases from the fruit had made their way into the air conditioning system, where they circulated thoughout the building and got the attention of the inhabitants. Though durian isn’t toxic, the fruit’s rancid remains are being dealt with by the Environment Protection Authority of Victoria.

Evacuating an entire building over some old produce may seem like an overreaction, but the room-clearing power of durian is taken seriously in other parts of the world. The fruit is banned in some hotels in Southeast Asia, and the Singapore subway famously posts signs warning passengers not to carry it onto trains.

[h/t Australian Associated Press]

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There's an Easy Way to Rid Your Mailbox of Catalogs and Other Junk
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You've signed up for paperless billing. You've opted in on e-statements for your credit cards. But your mailbox is still filled to the brim with envelopes full of useless credit card offers, catalogs, coupons, and charity solicitations. Thankfully, there is a way to take back your mailbox from unwanted junk mail—if you know where to go. According to The New York Times, there is a relatively painless way to reduce the amount of unwanted paper piling up in your mailbox.

DMAChoice.org is a website run by the DMA, or the Data & Marketing Association, a New York-based lobbying organization for data-based marketing and advertising that represents around 3600 companies that send direct mail to consumers, i.e., the sources of your junk mail. In order to try to keep consumers happy (and thus, more amenable to marketing), the website lets consumers opt out of certain categories of unsolicited mailings.

For a $2 registration fee, you can remove your name from mailing lists for catalogs, magazine offers, and other direct mail advertising. Your can opt out of offers from specific companies, like say, the magazine Birds and Blooms or the AARP, or you can opt out of all companies in a category. If you don't want to get any mail from DMA-affiliated businesses, you have to separately opt out of all three categories: magazine offers, all catalogs, and all "other" mail offers.

Compared to ripping up AARP offers every single day, the effort is worth it. For less than the price of a few stamps and a few minutes of your time, you can vastly cut down on your junk mail. While the opt-out only applies for companies that find their direct-mail potential customers through DMA lists, you'll still be eliminating a huge swath of your unwanted mail.

As for those annoying "prequalified" credit card offers, you'll have to go to a different website, but this one, at least, is free. OptOutPrescreen.com, run by the four major credit reporting agencies—Equifax, Innovis, Experian, and TransUnion—lets you opt out of all of credit card offers originating from the customer lists provided by those four reporting agencies. You can either file a request to opt out on the website to free yourself of credit card mailings for five years, or mail in an opt-out form to stop receiving them permanently. The site does ask you for your Social Security number, but it's legit, we promise. It has the FTC's stamp of approval.

[h/t The New York Times]

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