11 (number) "ùndici" (but in Spanish and Portuguese, 16, and in French, 17 is the first compound number), Chinese 十一 "shí yī", Korean 열한 "yeol han". 11 is a prime number. It is the smallest two-digit prime number in the decimal base. The next prime is 13, with which it comprises a twin prime. If a number is divisible by 11, reversing its digits will result in another multiple of 11. As long as no two adjacent digits of a number added together exceed 9, then multiplying the number by 11, reversing the digits of the product, and dividing that new number
Prime number of such a domain is the Gaussian integers formula_179, the ring of complex numbers of the form formula_180 where formula_181 denotes the imaginary unit and formula_34 and formula_35 are arbitrary integers. Its prime elements are known as Gaussian primes. Not every number that is prime among the integers remains prime in the Gaussian integers; for instance, the number 2 can be written as a product of the two Gaussian primes formula_184 and formula_185. Rational primes (the prime elements in the integers) congruent to 3 mod 4 are Gaussian primes, but rational primes congruent to 1 mod 4 are not. This