Math archives #5: What's the longest prime number? --with an update

First posted on November 11, 2011.  (11-11-11.  I just thought I'd mention that.)

What would we do without the Internet...

I mentioned recently that a quick check on the current population of Burundi--the subject of a French lesson--showed that there were way more people there than even the (fairly recent) teacher's guide suggested.  That lined up with the fact that we were heading for 7 billion people on Earth by the end of last month.

Today's math history lesson was about the Sieve of Eratosthenes, and the hunt for very large prime numbers.  John Tiner's 2001 book Exploring the World of Mathematics mentioned that the largest discovered to date was over 4 million digits long, which would take about a thousand pages to print out.

On a hunch that that fact too might have been updated, I looked it up.

Yes, the 4-million-digits longest prime was correct in 2001.  

But as of 2008, we are up to a number that is 12,978,189 digits long.

And you thought your ID numbers were hard to learn.

2014 Update from Wikipedia:  As of January 2014, the largest known prime number is 2^57,885,161 − 1, a number with 17,425,170 digits.  (Sourced from this article.)

There are more and more and more and more of us...

in the world. It's estimated that by the end of October, there will be 7 billion human beings on this planet.

According to the same Toronto Star article, and Wikipedia, we hit the 6 billion mark in 1999. Twelve years seems like a very short time to add a billion people.

When are we expected to hit 8 billion? 2027.

"“The world is currently in the midst of the greatest demographic upheaval in human history,” says David Bloom, professor of economics and demography at the Harvard School of Public Health."--Antonia Zerbisias, Toronto Star

Crayons and Mama Squirrel noticed something strange about population as well. In the Mission Monde French workbook, Crayons was asked to find the population of Burundi. She clicked on a couple of websites, and this is what she found: a 2009 estimate of 8,303,000 2009; and a July, 2011 count of 10,216,190.

The teacher's manual for the course, published in 2006 and re-edited in 2008, gives the population as 6,370,609.

Either someone miscounted, or the population of tiny little Burundi, one of the ten poorest countries in the world, is growing exponentially. WikiAnswers seems to agree with that fact, but we still don't have a clear answer as to why. We guessed that it might be an influx of refugees from famine-stricken areas, but that didn't seem logical either. Second guess: that it's just what the Toronto Star article is talking about, more babies born in the poorest parts of the world.

I don't pretend to have answers. I just read the papers. And the teacher's manual.