People knowledgeable of the meme may respond "nice" in response to the appearance of the number, whether intentionally an innuendo or not.
[9][10] 69 can be expressed as the sum of consecutive positive integers in multiple ways, making it a polite number.
[21][22][23] Visually, in Arabic numerals, 69 is a strobogrammatic number because it looks the same when viewed both right-side and upside down.
[24] 69 is a centered tetrahedral number, a figurate number that represents a pyramid with a triangular base and all other points arranged in layers above the base, forming a tetrahedron shape.
[29] This means to humorously imply that the reference to the sex position was intentional.