# Julia, 46 bytes

<!-- language-all: lang-julia -->

    n=int(ARGS[1]);show(sum([n%i==0for i=1:n])==2)

An integer is read as the first command line argument using `int(ARGS[1])` and the result is printed to STDOUT using `show`. Primality is checked using trial division with the same formulation as [my R answer](https://codegolf.stackexchange.com/a/57675/20469).

Note that the builtin function `isprime` uses the Miller-Rabin algorithm, which is probabilistic and is thus unsuitable for this challenge. (Thanks to Martin Büttner for pointing that out.)

Saved 4 bytes thanks to kvill.