Ramanujan number - taxi cab number - 1729

Ramanujan number - 1729
1729 = 1³ + 12³ = 9³ + 10³ (The 1729 is a smallest number that can be written as sum of 2 cubes, in 2 different ways.)
Taxi cab number
a^3 + b^3 = c^3 + d^3
(The 1729 is a second smallest number of taxi cab number. The first number is 2 = 1³ + 1³)

Note :
Other Interesting Facts of 1729 are,
1 + 7 + 2 + 9 = 19,
19 * 91 = 1729,
1729 is a Zeisel number,
1729 is also the third Carmichael number and the first absolute Euler pseudoprime (sphenic number),
1729 is a Harshad number.