There are many different numbering schemes for assigning numbers to entities. These generally require an agreed set of rules, or a central coordinator.
Numbering schemes include:
The E.164 numbering plan for telephone numbers, including:
... the population is spread out with 13.8% under the age of 18, 34.0% from 18 to 24, 17.6% from 25 to 44, 20.5% from 45 to 64, and 14.1% who are 65 years of age or older. ...