300 (number) nontotient. 315 = 3 × 5 × 7. 315 is a Harshad number 316 = 2 × 79. 316 is a centered triangular number and a centered heptagonal number 317 is a prime number, Eisenstein prime with no imaginary part, Chen prime, and a strictly non-palindromic number. 317 is also shorthand for the LM317 adjustable regulator chip. It is also the area code for the Indianapolis region. 318 = 2 × 3 × 53. It is a sphenic number, nontotient, and the sum of twelve consecutive primes (7 + 11 + 13 + 17 + 19 + 23 + 29
Prime number Several historical questions regarding prime numbers are still unsolved. These include Goldbach's conjecture, that every even integer greater than 2 can be expressed as the sum of two primes, and the twin prime conjecture, that there are infinitely many pairs of primes having just one even number between them. Such questions spurred the development of various branches of number theory, focusing on analytic or algebraic aspects of numbers. Primes are used in several routines in information technology, such as public-key cryptography, which relies on the difficulty of factoring large numbers into their prime factors. In abstract algebra, objects that behave