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 are distinct Fermat primes. Likewise, a regular formula_1-gon may be constructed using straightedge, compass, and an angle trisector if and only if the prime factors of formula_1 are any number of copies of 2 or 3 together with a (possibly empty) set of distinct Pierpont primes, primes of the form formula_241. It is possible to partition any convex polygon into formula_1 smaller convex polygons of equal area and equal perimeter, when formula_1 is a power of a prime number, but this is not known for other values of formula_1. Beginning with the work of Hugh Montgomery and Freeman Dyson in