13th root 13th root Extracting the 13th root of a number is a famous category for the mental calculation world records. The challenge consists of being given a large number (possibly over 100 digits) and asked to return the number that, when taken to the 13th power, equals the given number. For example, the 13th root of 8,192 is 2 and the 13th root of 96,889,010,407 is 7. Extracting the 13th root has certain properties. One is that the 13th root of a number is much smaller: a 13th root will have approximately 1/13th the number of digits. Thus, the 13th root
Digital root the digital root of formula_46 modulo 9. Especially, we can define the digital root of minus formula_1 as follows: The digital root of formula_45 × formula_46 is digital root of the product of the digital root of formula_45 and the digital root of formula_46. This article is about the digital root in decimal or base ten, hence it is the number mod 9. It is nothing different as the number converted to base 9 and then only the last digit taken. In other radixes the digital root is number mod (base-1) so in base 12 a digital root of a