I was able to retrieve the mobile number for all contacts using REST API, or for a given contact using AMPScript or Server Side Javascript.

• For all contacts, you can use:

GET: https://www.exacttargetapis.com/contacts/v1/attributeSets/name:MobileConnect%20Demographics?$page=

• To retrieve a single contact mobile i use this (being contactID the one of the contact you want the mobile):

var mobileConnectDE = DataExtension.Init("DATA_EXTENSION_EXTERNAL_KEY");

var rowMobileConnect = {};

try{
rowMobileConnect = mobileConnectDE.Rows.Lookup(['_ContactID'], [contactID]);
Write("Retrieve status: " + Stringify(rowMobileConnect));
for(var i in rowMobileConnect){
Write("MobileNumber: " + rowMobileConnect[i]['_MobileNumber']); }
} catch (ex) {
Write("An error has occurred retrieving rows: "

• Stringify(ex));
  return;
  }

You can put this piece of code in a landing page.

I was able to retrieve the mobile number for all contacts using REST API, or for a given contact using AMPScript or Server Side Javascript.

For all contacts, you can use:

GET: https://www.exacttargetapis.com/contacts/v1/attributeSets/name:MobileConnect%20Demographics?$page=<pageNo>

To retrieve a single contact mobile i use this (being contactID the one of the contact you want the mobile):

var mobileConnectDE = DataExtension.Init("DATA_EXTENSION_EXTERNAL_KEY");
var rowMobileConnect = {};
try {        
  rowMobileConnect = mobileConnectDE.Rows.Lookup(['_ContactID'], [***contactID***]);      
  Write("Retrieve status: " + Stringify(rowMobileConnect));

  for(var i in rowMobileConnect){      
     Write("MobileNumber: " + rowMobileConnect[i]['_MobileNumber']);
  }   
} catch (ex) { 
  Write("An error has occurred retrieving rows: " + Stringify(ex));  
  return; 
}

You can put this piece of code in a landing page.