diff --git a/PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs b/PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs
index 1e021a1..5ba86d0 100644
--- a/PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs
+++ b/PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs
@@ -177,12 +177,6 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
         bool lastIsSeven = (prime & 3UL) == 3UL;
         const ushort DecimalMaskWhenLastIsSeven = (1 << 3) | (1 << 7) | (1 << 9);
         const ushort DecimalMaskOtherwise = (1 << 1) | (1 << 3) | (1 << 9);
-        const byte AcceptableRemainder8Mask = 0b10000010;
-        const int NonZeroMod3Mask = 0b00000110;
-        const int NonZeroMod5Mask = 0b00011110;
-        const int NonZeroMod7Mask = 0b01111110;
-        const int NonZeroMod11Mask = 0b11111111110;
-        const int RequiredSmallPrimeMask = 0b1111;
 
         while (divisor.CompareTo(limit) <= 0)
         {
@@ -192,14 +186,12 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
             ushort decimalMask = lastIsSeven ? DecimalMaskWhenLastIsSeven : DecimalMaskOtherwise;
             bool admissible = ((decimalMask >> remainder10) & 1) != 0;
 
-            bool passesOctalMask = ((AcceptableRemainder8Mask >> remainder8) & 1) != 0;
-            int smallPrimeBits = ((NonZeroMod3Mask >> remainder3) & 1)
-                | (((NonZeroMod5Mask >> remainder5) & 1) << 1)
-                | (((NonZeroMod7Mask >> remainder7) & 1) << 2)
-                | (((NonZeroMod11Mask >> remainder11) & 1) << 3);
-            bool passesSmallPrimeMasks = (smallPrimeBits & RequiredSmallPrimeMask) == RequiredSmallPrimeMask;
-
-            if (admissible && passesOctalMask && passesSmallPrimeMasks)
+            if (admissible
+                && (remainder8 == 1 || remainder8 == 7)
+                && remainder3 != 0
+                && remainder5 != 0
+                && remainder7 != 0
+                && remainder11 != 0)
             {
                 MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(candidate);
                 ulong divisorCycle;
diff --git a/PerfectNumbers.Core/MersenneDivisorCycles.cs b/PerfectNumbers.Core/MersenneDivisorCycles.cs
index a349020..772fab8 100644
--- a/PerfectNumbers.Core/MersenneDivisorCycles.cs
+++ b/PerfectNumbers.Core/MersenneDivisorCycles.cs
@@ -58,11 +58,7 @@ public class MersenneDivisorCycles
             return true;
         }
 
-        const int InvalidParameterMask = 0b111;
-        int invalidBits = (exponent <= 1UL ? 1 : 0)
-            | ((divisor <= 1UL ? 1 : 0) << 1)
-            | ((int)(1UL ^ (divisor & 1UL)) << 2);
-        if ((invalidBits & InvalidParameterMask) != 0)
+        if (exponent <= 1UL || divisor <= 1UL || (divisor & 1UL) == 0UL)
         {
             return false;
         }
@@ -121,11 +117,7 @@ public class MersenneDivisorCycles
 
     private static bool IsValidMersenneDivisorCandidate(ulong divisor, ulong exponent)
     {
-        const int InvalidParameterMask = 0b111;
-        int invalidBits = (exponent <= 1UL ? 1 : 0)
-            | ((divisor <= 1UL ? 1 : 0) << 1)
-            | ((int)(1UL ^ (divisor & 1UL)) << 2);
-        if ((invalidBits & InvalidParameterMask) != 0)
+        if (exponent <= 1UL || divisor <= 1UL || (divisor & 1UL) == 0UL)
         {
             return false;
         }
diff --git a/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs b/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs
index 188af6d..ac93691 100644
--- a/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs
+++ b/PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs
@@ -188,9 +188,7 @@ internal static partial class PrimeOrderCalculator
 	private static ulong InitializeStartingOrderCpu(ulong prime, ulong phi, in MontgomeryDivisorData divisorData)
 	{
 		ulong order = phi;
-		const int AcceptablePrimeResidueMask = (1 << 1) | (1 << 7);
-		int residue = (int)(prime & 7UL);
-		if (((AcceptablePrimeResidueMask >> residue) & 1) != 0)
+		if ((prime & 7UL) == 1UL || (prime & 7UL) == 7UL)
 		{
 			ulong half = phi >> 1;
 			if (Pow2EqualsOneCpu(half, prime, divisorData))