Hoist prime order thresholds in CPU heuristics

PerfectNumbers.Core/DivisorGenerator.cs

@@ -8,31 +8,9 @@ internal static class DivisorGenerator
     private const ushort DecimalMaskOtherwise = (1 << 1) | (1 << 3) | (1 << 9);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static bool IsValidDivisor(
-        byte remainder10,
-        byte remainder8,
-        byte remainder3,
-        byte remainder5,
-        byte remainder7,
-        byte remainder11,
-        LastDigit lastDigit)
+    public static ushort GetDecimalMask(LastDigit lastDigit)
     {
-        ushort decimalMask = lastDigit == LastDigit.Seven ? DecimalMaskWhenLastIsSeven : DecimalMaskOtherwise;
-        if (((decimalMask >> remainder10) & 1) == 0)
-        {
-            return false;
-        }
-
-        if (remainder8 != 1 && remainder8 != 7)
-        {
-            return false;
-        }
-
-        if (remainder3 == 0 || remainder5 == 0 || remainder7 == 0 || remainder11 == 0)
-        {
-            return false;
-        }
-
-        return true;
+        return lastDigit == LastDigit.Seven ? DecimalMaskWhenLastIsSeven : DecimalMaskOtherwise;
     }
+
 }