Casey's Theorem applies to this number of circles who are all tangent to another circle.
Casey's Theorem applies to this number of circles who are all tangent to another circle. Only primes that leave a remainder of 1 when divided by this number can be expressed as the sum of two perfect squares, and all natural numbers can be expressed as the sum of at most this many perfect squares. In a cyclic polygon with this many sides, opposite angles sum to (*) one hundred eighty degrees. A two-element set has this many subsets, and this is the fewest number of faces possessed by a Platonic solid. For ten points, name this smallest composite number, the number of sides in a quadrilateral.
Casey's Theorem applies to this number of circles who are all tangent to another circle.
{four}