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
Turned A 19th century by Charles Sanders Peirce as a logical symbol for 'un-American' ("unamerican"). The symbol ∀ has the same shape as a capital turned A, sans-serif. It is used to represent universal quantification in predicate logic. When it appears in a formula together with a predicate variable, they are referred to as a "universal quantifier". In traffic engineering it is used to represent flow, the number of units (vehicles) passing a point in a unit of time. Turned A Turned A (capital: Ɐ, lowercase: ɐ, math symbol ∀) is a symbol based upon the letter A. Lowercase ɐ (in two