Primes / Is 13 prime?

Is 13 a Prime Number?

Yes

13 is prime: for 13, testing every prime up to √13 ≈ 3.6 (namely 2, 3) finds no divisor. 13 sits between primes 11 and 17, 2 below and 4 above. 13 shares no factor with 2-12; 13's divisors start beyond that range. 13 is odd, digit sum 4 for 13, digital root 4 for 13. 13 has 8 primes within 10 of 13.