# BigInteger.GreatestCommonDivisor Method

.NET Framework 4

Finds the greatest common divisor of two BigInteger values.

Namespace:  System.Numerics
Assembly:  System.Numerics (in System.Numerics.dll)

## Syntax

```public static BigInteger GreatestCommonDivisor(
BigInteger left,
BigInteger right
)
```

#### Parameters

left
Type: System.Numerics.BigInteger
The first value.
right
Type: System.Numerics.BigInteger
The second value.

#### Return Value

Type: System.Numerics.BigInteger
The greatest common divisor of left and right.

## Remarks

The greatest common divisor is the largest number into which the two BigInteger values can be divided without returning a remainder.

If the left and right parameters are non-zero numbers, the method always returns at least a value of 1 because all numbers can be divided by 1. If either parameter is zero, the method returns the absolute value of the non-zero parameter. If both values are zero, the method returns zero.

Note

Computing the greatest common divisor of very large values of left and right can be a very time-consuming operation.

The value returned by the GreatestCommonDivisor method is always positive regardless of the sign of the left and right parameters.

## Examples

The following example illustrates a call to the GreatestCommonDivisor method and the exception handling necessary to provide useful information about an ArgumentOutOfRangeException. The result indicates that the greatest common divisor of these two numbers is 1.

```
BigInteger n1 = BigInteger.Pow(154382190, 3);
BigInteger n2 = BigInteger.Multiply(1643590, 166935);
try
{
Console.WriteLine("The greatest common divisor of {0} and {1} is {2}.",
n1, n2, BigInteger.GreatestCommonDivisor(n1, n2));
}
catch (ArgumentOutOfRangeException e)
{
Console.WriteLine("Unable to calculate the greatest common divisor:");
Console.WriteLine("   {0} is an invalid value for {1}",
e.ActualValue, e.ParamName);
}

```

Supported in: 4

Supported in: 4

## Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.