23 pairs of chromosomes, which results in 46 chromosomes. 22 of the pairs are automsomes, while 1 pair in the sex chromosomes (which XX results in a female and XY results in a male).
I would like to clarify that sometimes people can have more or less than 46 chromosomes is not due to mutation, but rather nondisjunction. Basically it is caused by improper division of chromosomes during meiosis. The only time someone can survive from nondisjunction (result in a vilable baby) is when the person has an extra chromosomes 21, or an extra sex chromosomes. Also one may survive with only 1 X chromosome or missing part of chromosome 5.
Extra chromosome 21: Down Syndrome
Missing a partial Chromosome 5: Cri du chat Syndrome (aka Cat's Cry)
XXX: Tripe X Syndrome
X: Turner's Syndrome
XYY: XYY Syndrome
XXY: Klinefelter's Syndrome