
Inarithmetic andalgebra thesixth power of anumbern is the result of multiplying six instances ofn together. So:
Sixthpowers can be formed by multiplying a number by itsfifth power, multiplying thesquare of a number by itsfourth power, bycubing a square, or by squaring a cube.
The sequence of sixth powers ofintegers are:
They include the significantdecimal numbers 106 (amillion), 1006 (ashort-scale trillion and long-scale billion), 10006 (aquintillion and along-scale trillion) and so on.
The sixth powers of integers can be characterized as the numbers that are simultaneously squares and cubes.[1] In this way, they are analogous to two other classes offigurate numbers: thesquare triangular numbers, which are simultaneously square and triangular,and the solutions to thecannonball problem, which are simultaneously square and square-pyramidal.
Because of their connection to squares and cubes, sixth powers play an important role in the study of theMordell curves, which areelliptic curves of the form
When is divisible by a sixth power, this equation can be reduced by dividing by that power to give a simpler equation of the same form.A well-known result innumber theory,proven byRudolf Fueter andLouis J. Mordell, states that, when is an integer that is not divisible by a sixth power (other than the exceptional cases and), this equation either has norational solutions with both and nonzero or infinitely many of them.[2]
In thearchaic notation ofRobert Recorde, the sixth power of a number was called the "zenzicube", meaning the square of a cube. Similarly, the notation for sixth powers used in 12th centuryIndian mathematics byBhāskara II also called them either the square of a cube or the cube of a square.[3]
There are numerous known examples of sixth powers that can be expressed as the sum of seven other sixth powers, but no examples are yet known of a sixth power expressible as the sum of just six sixth powers.[4] This makes it unique among the powers with exponentk = 1, 2, ... , 8, the others of which can each be expressed as the sum ofk otherk-th powers, and some of which (in violation ofEuler's sum of powers conjecture) can be expressed as a sum of even fewerk-th powers.
In connection withWaring's problem, every sufficiently large integer can be represented as a sum of at most 24 sixth powers of integers.[5]
There are infinitely many different nontrivial solutions to theDiophantine equation[6]
It has not been proven whether the equation
has a nontrivial solution,[7] but theLander, Parkin, and Selfridge conjecture would imply that it does not.