All irrational numbers can be written as continued fractions, like the one below.

It turns out that, as N approaches infinity, the geometric mean of the first N a_i coefficients converges to a constant called Khinchin's constant for almost all (i.e., all but a Lebesgue null set of) numbers. This property can be called Khinchin;s property.

Although almost all numbers have this property, and some well-known constants, including π, are believed to have it, there are no natural examples of numbers that have been proven to have it.