Converting long string of binary to hex c#

I'm looking for a way to convert a long string of binary to a hex string.

the binary string looks something like this "0110011010010111001001110101011100110100001101101000011001010110001101101011"

I've tried using

hex = String.Format("{0:X2}", Convert.ToUInt64(hex, 2));

but that only works if the binary string fits into a Uint64 which if the string is long enough it won't.

is there another way to convert a string of binary into hex?

Thanks