11 (number) is divisible by eleven. This also works by adding a trailing zero instead of a leading one: 65 + 63 + 70 = 198, which is divisible by 11. This also works with larger groups of digits, providing that each group has an even number of digits (not all groups have to have the same number of digits). An easy way of multiplying numbers by 11 in base 10 is: If the number has: In base 13 and higher bases (such as hexadecimal), 11 is represented as B, where ten is A. In duodecimal, however, 11 is sometimes represented as
Prime number examples of prime-generating formulas come from Mills' theorem and a theorem of Wright. These assert that there are real constants formula_51 and formula_52 such that are prime for any natural number formula_1 in the first formula, and any number of exponents in the second formula. Here formula_55 represents the floor function, the largest integer less than or equal to the number in question. However, these are not useful for generating primes, as the primes must be generated first in order to compute the values of formula_56 or formula_52. Many conjectures revolving about primes have been posed. Often having an elementary