That value is far too large to store in a double without loss of precision. You will need to use a custom data class, a symbolic variable, or store the output digits in a char vector. If you are okay with having the output digits in a char vector then you can download John D'Errico's excellent base2base function:
>> base2base('DB7C2ABF62E35E668076BEAD208B',16,10)
ans = 4451685225093714772084598273548427
You could easily convert the output of base2base to a symbolic variable.
