aP$-1=1($mod p$)$ for al integers a and primes p$.$

b$.$ aP$-1=1($mod p$)$ for al integers a such that a # $0($mod p$)$ for a prime p$.$ c$.4($n$)<=$ n for all n $$ Z$+.$

d$.$q$($n$)<=$n$-1$foralln$$Z$+.$

e$.$ The units ni Z$,$ are hte positive integers less than n and relatively prime to n$..$f The product of two units ni Z$,$ si always a unit.

g$.$ The product of two nonunits ni Z$,$ may be a unit.

h$.$ The product of a unit and a nonunit ni Z$,$ is never a unit.