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
Gear Cube Pyraminx, or even the Gear Cube. They are most likely using "Singmaster notation", originally developed by David Singmaster. It allows for algorithms to be written in a way that a solver can use it no matter what side of the cube they are on. When a prime symbol ( ' ) follows a letter it indicates that move must be rotated in a counter-clockwise fashion. However, if the prime symbol is absent after the letter, that move must be rotated in a clock-wise fashion. For example: R - rotate the right side clockwise. R' - rotate the right side counter-clockwise.