Strobogrammatic number Strobogrammatic number A strobogrammatic number is a number whose numeral is rotationally symmetric, so that it appears the same when rotated 180 degrees. In other words, the numeral looks the same right-side up and upside down (e.g., 69, 96, 1001). A strobogrammatic prime is a strobogrammatic number that is also a prime number, i.e., a number that is only divisible by one and itself (e.g., 11). It is a type of ambigram, words and numbers that retain their meaning when viewed from a different perspective, such as palindromes. When written using standard characters (ASCII), the numbers, 0, 1, 8 are
Prime (symbol) to subscripts – "x"′ generally means something related to or derived from "x". For example, if a point is represented by the Cartesian coordinates , then that point rotated, translated or reflected might be represented as . The prime symbol is not related to prime numbers. Usually, the meaning of "x"′ is defined when it is first used, but sometimes its meaning is assumed to be understood: The prime is said to "decorate" the letter to which it applies. The same convention is adopted in functional programming, particularly in Haskell. In geometry, geography and astronomy, prime and double prime are