Yes, but I'm not sure why you would want it. Hit your speed dial #1 and it might display the number on the screen when it calls your voicemail, if not check the recent call log or dialed calls to see the number that it dialed to go to voicemail. Or, on some phones you can check to see what numbers are stored for each speed dial, check and see what number is stored for #1.
On all my GSM phones, and they have different phone numbers, they all call the 'same' regional/semi-local number +14802252975 when I speed dial #1 (your area probably uses a different access number unless you live in my region of the country) and it sends me to the correct mailbox based on the phone I'm calling from. On my CDMA phones they all dial the *86 which does the same as the GSM regional/semi-local number for the CDMA network. I answered your question, those are the numbers my phones dial to access voicemail but I'm sure thats not what you're interested in. What are you trying to do with it? Are you trying to use GSM codes to redirect calls destined for your voicemail or something else?
FYI: If I call the GSM number +14802252975 from my CDMA phone it answers with "Welcome to AT&T voicemail, to access your voicemail we need more information ......".