**FORMAL NUMBERS**

**"God created the integers, all else is
the work of man..."**

**We first recall the basic facts about the
different families of numbers which are at the beginning of all mathematical
constructions in number theory. Different extensions of the notion of number
exist. An old one is the notion of complex number which is widely
known and very useful for physical sciences. Another and more recent one
is the notion of p-adic number based upon a prime number p.
Here we are considering a different kind of numbers which are also, but in a different way, closely related to prime numbers. **