Simple prime number test 1000 slower than trivial python?

New to Julia
4

Actually, you need to take care here. Firstly, your input value is so large that it’s not an Int, it’s an Int128:

julia> typeof(10000001829379821798314198278324234)
Int128

The square root is not outside the range of Int64, but with larger inputs you can get into trouble.

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
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