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
Legendre symbol alternative expressions for the Legendre symbol were devised in order to produce various proofs of the quadratic reciprocity law. The above properties, including the law of quadratic reciprocity, can be used to evaluate any Legendre symbol. For example: Or using a more efficient computation: The article Jacobi symbol has more examples of Legendre symbol manipulation. Legendre symbol In number theory, the Legendre symbol is a multiplicative function with values 1, −1, 0 that is a quadratic character modulo an odd prime number "p": its value on a (nonzero) quadratic residue mod "p" is 1 and on a non-quadratic residue ("non-residue")