46 for diploid(full set). 23 for haploid(half set)
cells with haploid number are sex cells because they need only have to fuse with another sex cell to make a zygote(to a fetus).
somatic cells(body cells other than sex cells) replace each other regularly because they die regularly-thousands a day. somatic cells have a diploid number of chromosomes because the cell needs all of the chromosomes to do it's job properly.
so, sex cells-match up with other sex cells to make full set of chromosomes
and somatic cells replace the old somatic cells-so a full set is needed to make a whole new cell