Visual C++ :: Decoding RFID Data Hexadecimal Math

I currently am stuck at getting the needed outcome data from my RFID card. I got it decoded but now I need to do a few more things in order to get the final card number off the back of the card.

The cryptic value was E********B**0**E** (covered to protect card)

Decrypting it turned into 0000003048D1263B

Now I have 3 more steps to take in order to get to my wanted card number.

Step 1) Mask off the lower 20-bits (which should give me 0x1263B) I am unsure of how to go about doing that using C++.

Step 2) Divide by 2 to strip off the lower parity bit (which should be 0x931d). And again, I'm unsure of how to go about doing this in C++.

Step 3) Convert hexadecimal value to decimal value (which would equal my wanted card number). This should be easily done using C++ at this point - though hard to confirm that since I am on step 1).

Code:
const char* original = "0x931d";
unsigned long n = std::strtoul(original, nullptr, 16);

All of this looks to me like RegEX does to most people - complicated and not understanding why it does what it does but gives the correct output.