Primes / Is 401 prime?

Is 401 a Prime Number?

Yes

401 is prime: for 401, testing every prime up to √401 ≈ 20.0 (namely 2, 3, 5, 7, 11, 13, 17, 19) finds no divisor. 401 sits between primes 397 and 409, 4 below and 8 above. 401 shares no factor with 2-12; 401's divisors start beyond that range. 401 is odd, digit sum 5 for 401, digital root 5 for 401. 401 has 3 primes within 10 of 401.