Reduce allocations and refactoring

src/Julia/Problems001-050/Problem016.jl

@@ -10,13 +10,19 @@ https://projecteuler.net/problem=16 =#
 
 using BenchmarkTools
 
+# function pow(n)
+#     return 2^BigInt(n)
+# end
+
 function Problem16()
     #=
     2^15 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.
 
     What is the sum of the digits of the number 2^1000? =#
-    n = 1000
-    return sum(parse(Int, d) for d in string(2^BigInt(n)))
+
+    n::Int16 = 1_000
+
+    return sum(digits(2^BigInt(n)))
 end