unsigned short

Et bien je dirais que ce serait :
unsigned short chiffre = 0;
le type qui se rapproche le plus de la definition d'un chiffre ([0;9]).

Ensuite, au niveau de la depense de memoire :

Type__________________________Size
bool..........................................................1 byte
char, unsigned char, signed char....1 byte
short, unsigned short...........................2 bytes
int, unsigned int....................................4 bytes
long, unsigned long.............................4 bytes
float..........................................................4 bytes
double.....................................................8 bytes