36 (number) 36 (number) 36 (thirty-six) is the natural number following 35 and preceding 37. 36 is both the square of six and a triangular number, making it a square triangular number. It is the smallest square triangular number other than one, and it is also the only triangular number other than one whose square root is also a triangular number. It is also a circular number- a square number that ends with the same integer by itself (6×6=36). It is the smallest number "n" with exactly eight solutions to the equation φ("x") = "n". Being the smallest number with exactly nine
Square root of a matrix is the unique positive square root of the positive operator "A""A", and "U" is defined by . If "A" is not invertible, then it still has a polar composition in which "P" is defined in the same way (and is unique). The unitary operator "U" is not unique. Rather it is possible to determine a "natural" unitary operator as follows: "AP" is a unitary operator from the range of "A" to itself, which can be extended by the identity on the kernel of "A". The resulting unitary operator "U" then yields the polar decomposition of "A". By Choi's result, a