A mobile number's numerology is its digits added together and reduced to a single root, from 1 to 9. This tool computes that root and its ruling planet, and if you add your date of birth it also compares the root with your Mulank. Letters are not involved: a phone number is read on its digits alone, and the country or operator prefix counts as part of the total.
Every digit counts once, and separators do not. For 98765 43210 the digits add to 45, and 45 reduces to 9, so the root is 9 and its planet in this app's table is Mars. Including or dropping a country code changes the total and can change the root, which is why the tool shows the sum before the reduction.
This is the one place where mobile numbers behave differently from the other things people run through the same arithmetic. A vehicle plate or a flat number carries letters, and Indian practice converts those letters through the Chaldean table and adds them in. A mobile number has no letters, so the digits-only reading is complete rather than a simplification.
With no birth date, the tool falls back on the general reading in common use: roots 1, 3, 5, 6 and 9 are treated as supportive, 4 and 8 as challenging, and the rest as neutral. That is a statement about a widespread convention, not about you, and the page says so.
Give a date of birth and the verdict becomes comparative instead: the tool computes your Mulank from the day of birth and checks whether the phone root is the same number or one of its friendly numbers. AstroZivi is explicit that this friendship grid has no located source of any kind, and that it is not the planetary friendship scheme of Brihat Parashara Hora Shastra ch. 3, which disagrees with it. The verdict is shown for what it is: common modern practice.
The practical use is comparison, not prophecy. If you are choosing between two numbers a shop is offering, running both takes a few seconds and tells you which root each carries and how each sits with your Mulank. That is a small, honest input into a decision that has better reasons on either side.
It is worth keeping the scale in mind. A root number sorts every phone number in the world into nine groups, so any statement attached to a root is a statement about roughly one ninth of all numbers. AstroZivi computes the arithmetic exactly and declines to dress that up as a forecast.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.