As you know, in the world of mathematics prime numbers are those that are only divisible by 1 and by themselves, but to make it clearer, Prime Integer Observatory has been created.
Prime Integer Observatory generates a table where it shows you all integers and numbers by which they are divisible. In this way you will verify, for example, that 13 is a cousin, because it can only be divided by 1 and by itself (13); on the other hand, 21 is not, because it is divisible by 1, 3, 7 and 21.
The range of numbers to be displayed is decided by the user. Prime Integer Observatory is totally free.
You can free download Prime Integer Observatory 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.