# Ramanujan Number

When you love mathematics you can see magic in numbers. Your face gets lit up when you observe something new about a number. Something similar and very interesting happened with great Indian mathematician ** **

You can see the title of this post is **Ramanujan Number**. You might have already guessed that he might have a stumbled up on some very interesting number with some peculiar characteristics. If you have guessed that, you are right. Ramanujan number is **1729. **

**1729** is also known as the **Hardy – Ramanujan number**** ****. **This number is also called the Taxicab number.

**Ramanujan number** is so named after a famous anecdote of the British mathematician G. H. Hardy regarding a hospital visit to the Indian mathematician Srinivasa Ramanujan.

In Hardy’s own 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 positive cubes in two different ways.”

The numbers is such that,

1729 = 1^3 + 12^3 = 9^3 + 10^3

**Some observations** **related to Ramanujan Number**–

- If negative cubes are allowed, 91 is the smallest possible number with similar quality 91 = 6^3 + (?5)^3 = 4^3 + 3^3
- Interestingly 91 is also a factor of 1729. (91×19=1729)
- If taking “positive cubes” would not have been a condition, Ramanujan number could have been ?91, ?189, ?1729, and further negative numbers
- 1729 is also the third Carmichael number and the first absolute Euler pseudoprime. (If you want to know more about this numbers I can discuss it in some other post)
- Masahiko Fujiwara showed that 1729 is one of four positive integers (with the others being 81, 1458, and the trivial case 1) which, when its digits are added together, produces a sum which, when multiplied by its reversal, yields the original number: 1 + 7 + 2 + 9 = 19; 19 x 91 = 1729
- Till date only 10 Taxicab numbers are known. Subsequent Taxicab numbers are found using computers.

Friend’s there are many other properties attached to this great number suggested by various great mathematicians. If you could observe anything special about this number, leave a comment below to delight us.

Good morning sir it is really an excellent collection of an indian mathematician when i am reading the article i felt very proud being an indian sir please keep sending the updations related to our incredible indians

[...] 1729 is popularly called Ramanujan Number. Click to know more about Ramanujan Number [...]

sooooo good

U can also add his characteristics.

very nice.but i want some interesting topics plz send to my e-mail……..thank u

well written. but, it will be a complete if, more numbers are added( at least 10 numbers) .pls. send me some more numbers to my id(mkkarthik245@yahoo.com mkkarthik245@gmail.com)

HELLO! FREINDS

I WANT TO KNOW THE MAXIMUM RAMANUJAN NUMBERS

SENT IT ON MY ID!

give little more information about it

To know more about Ramanujan, you can read this – http://en.wikipedia.org/wiki/Srinivasa_Ramanujan

This book on S. Ramanujan is also a very good read – http://www.flipkart.com/books/8129103504?affid=INVineeblo

ramanujam the great scientist

You can add a small history of ramanujam in the beginning.

But anyway it’s good

[...] Palindromes , Munchausen Number, beauty of numbers, Ramanujan Number [...]

i want to know relation between ramanujam and pythagorean number

i need various explanation of ramanujam number.. please kindly send to my mail id

If you have some specific question, please let me know. I would love to answer it.

You can also get this book on S. Ramanujan – http://www.flipkart.com/books/8129103504?affid=INVineeblo

CAN YOU GIVE SOME DETAILED INFORMATION ABOUT IT I HAVE TO WRITE AN ARTICLE ON THIS TOPIC (ramanujan’s number)

You can get lot of information on this on wikipedia – here’s the link

http://en.wikipedia.org/wiki/1729_(number)

You can also get this book on S. Ramanujan – http://www.flipkart.com/books/8129103504?affid=INVineeblo

i need 10 hardy ramanujan numbers and their significants

lovely,, so good

love it

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love it

lovely

please tell me about ramanujan number

what are the new findings about ramanujan number

i want to know about all taxicab number. and please tell me the reason why ramanujan number famouse? (in detail)

reply in my email

[...] 1729 Hardy-Ramanujan's number [...]

My cousin recommended this blog and she was totally right keep up the fantastic work!

I know many more numbers which can be expressed as a sum of two cubes in two different ways.

My cousin recommended this blog and she was totally right keep up the fantastic work!

very good

do any combination, u will find the same nos. again & again

(add, subtract………..)