Primes / Is 421 prime?

Is 421 a Prime Number?

Yes

421 is prime: for 421, testing every prime up to √421 ≈ 20.5 (namely 2, 3, 5, 7, 11, 13, 17, 19) finds no divisor. 421 sits between primes 419 and 431, 2 below and 10 above. 421 shares no factor with 2-12; 421's divisors start beyond that range. 421 is odd, digit sum 7 for 421, digital root 7 for 421. 421 has 3 primes within 10 of 421.