Saturday, January 7, 2012

1729

You might have noticed that the url of my blog in aki1729.blogspot.com. In case you are wondering what 1729 stands for - it is the Hardy-Ramanujan's number. I do not remember how I came across this number, but it is indeed a very interesting number.

After a famous anecdote of the British mathematician G. H. Hardy regarding a hospital visit to the Indian mathematician Srinivasa Ramanujan. In Hardy's words:

"I remember once going to see him when he was ill at Putney. I had ridden in taxi cab number 1729 and remarked that the number seemed to me rather a dull one, and that I hoped it was not an unfavorable omen. "No," he replied, "it is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways."
~ source - wikipedia


What Ramanujan meant by  - "the smallest number expressible as the sum of two cubes in two different ways" is:

1729 = 13 + 123 = 93 + 103

Another interesting property of the number is this:

By adding all its digits we get : 1 + 7 + 2 + 9 = 19
By multiplying the sum with its reverse we get : 19 * 91 = 1729. Voila!

Just in case you are wondering, a mathematician named Masahiko Fujiwara found that property, not me.
There are other interesting properties of this number, but I am afraid things might get a little too mathematical, so I'll leave it here.

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