The purpose of this article is to introduce the concept of invariance and its properties. These properties can be used to check the primality of a number. Combining these properties with the Euler theorem, it is possible to generalize this theorem for all the values of $a^{ \varphi(m)}$ where $0 < a < m { \pmod { m}}$ independently if a is co prime or not with m. As $a^{ \varphi(m)+1} \equiv a$ if $m = a \cdot b$ and $GCD(a, b) = 1$. As the following steps, a new hypothesis is formulated regarding the substitution of the Totien function for an equivalent function that explains the Carmichael numbers. Keywords: Prime Numbers, Compound Numbers, Primality test, Euler theorem
Categories: math.NT