Suppose you were born on 21 July 1997.
Simply add all digits of your birth date only, in the above case Birth date is 21, therefore
Add both these singular number i.e. 2 + 1
It is equal to 3
or
birth date is 21 = 2 + 1 = 3 (Three)
in case born between the dates 1 to 9, the birth date becomes the birth number.
For the above case, you can check from the singular number section under the head Numerology, what are the signification of Number 3. Or your birth number which you derived from above method
You will find that most of the traits mentioned therein, apply on your personality.