Base64 to Bignum mystery

Here's my problem: I have a Base64 encoded prime number (128 bytes):

C# Base64 encoded byte[]:

0hro1m5sazztDrPfGibJG97tATwX2EnTDsMJgT5NN5nybbDUlOguxh6p/ccLtcvK8uXxioNklPWOZ8bWFkgMN6fyMGEB/J8PR2j5yXk8K+F2sLfJebQGXT6DVoaj8LhCDGg0yxeTA4be2rKwfdRzRJpIuqsxYoa0IQUkddE0zTs=

Java Base64 encoded byte[]:

ANIa6NZubGs87Q6z3xomyRve7QE8F9hJ0w7DCYE+TTeZ8m2w1JToLsYeqf3HC7XLyvLl8YqDZJT1jmfG1hZIDDen8jBhAfyfD0do+cl5PCvhdrC3yXm0Bl0+g1aGo/C4QgxoNMsXkwOG3tqysH3Uc0SaSLqrMWKGtCEFJHXRNM07

Note that the above encodings represent the following big integer:

147540829457233765072451123330814771849279870508740658191364766390571127595133276091294946062334381927384270351919254939797952329145575009188956176344993292905052474988906261438800251337646245695529118629813762877963253295780055957721171296243452181910303437299543284160580397044072404446659484077705433238843

In Java I can get the correct BigInteger by ensuring the signum is set to 1 in the constructor after decoding the Base64 representation:

BigInteger bob = new BigInteger(1, decoded)

C# requires you to change the byte order to big endian then stick in a BitInteger.

Creating a Bignum representation in Ruby is being a pain as a result (I think):

bites = Base64.decode64 value

res = bites.unpack("L*")

puts res

Output (C# Base64 encoded bytep[]):

35249789021852599100397716374343874946737400743004000506432476629771045247897406727496424982442945144570311964635624075155850220440702923891657823738204712817667169333330071198062025203398652919912928732041841245104879475827504620182081558513955106623738874544211107514025884576438285405965539851413509898555

Output (Java Base64 encoded byte[]):

137694483597560939102216875537430330334675944971008195657354096000921683438632582801840356652855833238983653339433419340491620923238667724119750598359178446093375339216275201592563381693380165675378265208733801963581564377942225889093611081093643407319811226275192229610364031150961850287214042230220628841976644813