Calculating a large sum of positive and negative integers gives wrong answer

[DNF]

Just a few comments:

@SherlockSage

for p in primes(floor(Int32, sqrt(Int64(max_n))))

Are you on a 32-bit system, because on mine, there’s no primes method for Int32:

julia> primes(Int32(11))
ERROR: MethodError: no method matching primes(::Int32)

Closest candidates are:
  primes(::Int64)
   @ Primes C:\Users\DNF\.julia\packages\Primes\Yo1YT\src\Primes.jl:130
  primes(::Int64, ::Int64)
   @ Primes C:\Users\DNF\.julia\packages\Primes\Yo1YT\src\Primes.jl:114

I was wondering why you wrapped your literals like this: Int64(2), since that’s not normally needed.

Secondly, it’s safer to use isqrt(n) rather than floor(Int, sqrt(n)). I struggled a bit to find an example, but here’s one from an old thread using an Int128:

@DNF

And secondly: Int(floor(sqrt(n))), gives you the wrong number:

julia> n = 10000001829379821798314198278324234
10000001829379821798314198278324234

julia> Int(floor(sqrt(n)))  # you should rather use floor(Int, sqrt(n)), actually
100000009146898688

julia> isqrt(n) # this is the largest integer m such that m^2 < n
100000009146898690