1729

(also called the Hardy-Ramanujan number) is the integer between.

Math features

 * 1729 is an odd number.
 * 1729 is a taxicab number. It is the first number being the sum of 2 positive cubes in 2 different ways. If negative cubes are allowed, numbers such as 91 or -1729 are included.
 * 1729 is the third Carmichael number, after 561 and 1105.
 * 1729 is the first number where it is the sum of 2 cubes in 2 different ways. 635318657 is the first number where it is the sum of 2 fourth powers in 2 different ways.
 * 1729 is a deficient number.
 * 1729 is also a Harshad number, since it is divisible by 1 + 7 + 2 + 9 = 19.
 * The 1729th decimal place is the start of all 10 digits consecutively in e.