Difference between federal and city number
Today, the quality of communication services is at a fairly high level. Now, in order to contact the desired subscriber, you will need to get your own device out of your pocket and dial the desired number. It may seem very strange to some of you, but an increasing number of consumers are interested in “beautifying” their own phone number.
I think each of you understands that by these words, we mean such a beautiful combination of numbers that they could be remembered by you and any other subscriber dialing your number for the maximum possible period of time. The relevance of the latter is quite conditioned. In particular, this state of affairs applies to all kinds of private institutions and enterprises. 
For them, the presence of a "beautiful" number is mandatory, because only in this way they would be able to find their place in the memory of those people who, after, will act as their potential customers. At the same time, one should understand that it is not always possible to choose any number you like, because at the present time, it is customary to distinguish between such concepts as “city” and “federal” numbers.
Why do we need city and federal numbers and in what situations are they used?
It should be noted that today, any number that is assigned to a particular subscriber is federal. Nevertheless, the overwhelming majority of modern providers, for some reason, divide phones into federal and city numbers. Of course, they still have some distinctive features in themselves, it would hardly be otherwise, they were distinguished from each other, in general. In this case, the essence of these distinctive features will be that the federal number must always begin with the number +7, followed by a combination of seven digits. As for the "city" numbers, they, in the conditions of our modern society, have ceased to be used in relation to landline phones alone.
Now, a number of this type, you will be able to offer to rent any modern mobile operator. By the way, in some cases, the provider of IP-telephony can also act as the latter. The city number can always be presented in the federal format as well. In such a case, it should start with an 8 followed by the code of the specific city. The latter, you can always choose, guided by the services of any operator.
It is quite possible that some of you will be surprised by this, but often a wide range of various numbers, or rather its availability, directly depends on the "toughness" of a particular mobile operator. The city number itself will directly depend on how large the number of subscribers is provided for in a particular municipal telephone network (it can have a seven-, six- or five-digit format).
Recently, many modern providers provide their customers with the opportunity to acquire so-called "short" telephone numbers. If you use them, you can dial numbers in six- or seven-digit format, not only from landlines, but also from mobile phones. Indeed, they are somewhat similar to ordinary "city" numbers. However, in the case of him, SMS will go to the full version of the number. Moreover, from you they will be displayed in a natural federal format for the operator. 
Thus, you can get such a federal number that would be presented in a city format. In view of this, if you need to acquire an ordinary city number, then in this case, a short number will certainly not suit you.
conclusions
The main and almost the only difference between a city number and the one that is now commonly called federal is precisely the number of their digits. So, in the event that the federal number got its name for the simple reason that it starts with the federal code of a certain mobile operator, then the city number starts with an eight, followed by the code of a particular city. For personal communication, it does not matter whether you give your preference to a federal or city number. At the same time, a certain difference can be provided for in business communication.
