Digital root number is the number mod 11 (Ɛ), for example, 1972 is 1 + 9 + 7 + 2 = 19 = 17 which is 1 + 7 = 8, while in decimal the root of the same number (3110) is 5; and in base 16 a digital root of a number is the number mod 15 (0xF), for example, 0x7DF is 7 + 13 + 15 = 35 = 0x23 which is 2 + 3 = 5, while in decimal the root of the same number (2015) is 8. Digital roots form an important mechanic in the visual novel adventure
Primitive root modulo n adding up elements of this multiplicative group? As it happens, sums (or differences) of two primitive roots add up to all elements of the index 2 subgroup of Z/"n" Z for even "n", and to the whole group Z/"n" Z when "n" is odd: No simple general formula to compute primitive roots modulo "n" is known. There are however methods to locate a primitive root that are faster than simply trying out all candidates. If the multiplicative order of a number "m" modulo "n" is equal to formula_2 (the order of Z), then it is a primitive root. In fact