Whether to store all numbers or just their ranges in database for this application

I'm developing a (PHP MySQL) Web App which will sell dynamically generated real time cell phone numbers for cellular companies. A company will ask for, say, a thousand numbers and this app will check for available numbers and provide them.

The number will be an 8 digit figure. The first two digits of the number will mostly be fixed as specific codes for a particular company, rest of the digits will be dynamically generated.

My question is whether

a) I should store all the sold numbers in database, if yes then:
   i)  Separate number in separate row or
   ii) All the numbers in a single row

b) Should store range of numbers i.e 32500001-32510000

Keeping performance and ease of handling the algorithm in mind, kindly suggest me your solution.