Unity C# BigIntegerメモ

int costTapItemLvCoefficient
int exponentiatio

// NG
returnBigInt =　new BigInteger( ( ((costTapItemLvCoefficient * exponentiation) * bonusCoefficient)  ).ToString(), 10);

結果：-1121583104

// NG
returnBigInt = (costTapItemLvCoefficient * exponentiation) * 131072;

結果：-1121583104

// OK 
returnBigInt = costTapItemLvCoefficient * exponentiation;
returnBigInt = returnBigInt * 131072;

結果：3173384192

C# int 上限

int -2,147,483,648 ～ 2,147,483,647
※参考：https://docs.microsoft.com/ja-jp/dotnet/csharp/language-reference/keywords/integral-types-table

追記

BigInteger returnBigInt =　new BigInteger("0",10);
int costTapItemLvCoefficient = 41152264;
int exponentiation = 205;


returnBigInt = costTapItemLvCoefficient * exponentiation;

// NG これも上限超えのマイナスになった。。
Debug.Log("returnBigInt " + returnBigInt.ToString());

BigInteger returnBigInt =　new BigInteger("0",10);
int costTapItemLvCoefficient = 41152264;
int exponentiation = 205;

returnBigInt = costTapItemLvCoefficient;
returnBigInt = returnBigInt * exponentiation;

// OK 挙動がよくわからない。。
Debug.Log("returnBigInt " + returnBigInt.ToString());

試した環境

MacOS Siera