## Archive for April 6th, 2011

### Twelves

April 6, 2011

The number 1729 has a right to be proud :  it initially had only a small role on a taxicab in England but its super-power of being the sum of  two positive cubes in not one but two ways (13+123 and 93+103) led to a big break in a Feature Story starring GH Hardy and Srinivasa Ramanujan, with follow-up appearances for years to come on the likes of Futurama and Proof.  So, you know, yay 1729.

But lest this Hardy-Ramanjuan number get too boastful, it’s not the only sequin at the Oscars.  Its neighbor, that unassuming 1728, turns out to be an interesting character in its own right.

The origin of this is in the dozen.  Although ten is a pretty natural base to use, in the sense that a lot of cultures break numbers up by tens in some form, it’s not the only possibility.   We have not only a special word for 12 (dozen), but a special word for 122 (gross), which suggests that our language carries hints of a Base 12 system.  And that leads to the question:  is there a special name for 123?

There is!  The official name is a Great Gross.   And while dozen and gross show up in egg cartons, it’s in measurement that the great gross really shines:  there are a dozen inches in a foot, a gross square inches in a square foot, and a great gross cubic inches in a cubic foot.

But while the great gross is helping out with set design, there’s a rumor (which we’re apparently happy to help spread) that 1728 actually has a stage name.  That’s because there’s a theorem about L-functions of elliptic curves called the Gross-Zagier Theorem, named after Benedict Gross and Don Zagier.  So the natural extension of a gross is…a Zagier!  Or at least that’s the name that 1728 goes by on the cocktail circuit according to Wikipedia, our local gossip rag.  Which makes us wonder where this down-to-earth yet whimsical number will show up next.

In an amusing turn of events, it turns out that Gross and Zagier won the Frank Nelson Cole prize in Number Theory in 1987 from the American Mathematical Society for their paper “Heegner points and derivatives of L-series” which contained the above theorem.  The other winner that year for a different paper was Dorian M. Goldfeld who, the following year, published a paper with M. Anshel entitled “Applications of the Hardy-Ramanujan partition theory to linear diophantine problems,” bringing it all back full-circles to the people who made 1729 famous.   It’s like one giant family reunion.