Primes / Is 311 prime?

Is 311 a Prime Number?

Yes

311 is prime: for 311, testing every prime up to √311 ≈ 17.6 (namely 2, 3, 5, 7, 11, 13, 17) finds no divisor. 311 sits between primes 307 and 313, 4 below and 2 above. 311 shares no factor with 2-12; 311's divisors start beyond that range. 311 is odd, digit sum 5 for 311, digital root 5 for 311. 311 has 4 primes within 10 of 311.