Perfect power
A positive integer is a perfect power if there exist integers
such that
and
. In particular,
is said to be a perfect
th power. For example,
, so
is a perfect
nd,
rd and
th power.
We restrict only because "being a perfect
st power" is a meaningless property: every integer is a
st power of itself.
Perfect second powers are also known as perfect squares and perfect third powers are also known as perfect cubes. This is because the area of a square and the volume of a cube is equal to the second and third powers of a side length, respectively.