How many 5-letter passwords can be created if no letter can be used twice within the password?

26*25*24*23*22=7893600

or you can use

26! / (26-5) !=7893600

If there are 5 letters used only, then 5! or 5*4*3*2 = 120

If all 26 letters of the alphabet may be used for the code, then:

26*25*24*23*22

If you mean letters of the alphabet, and not case sensitive, it's 26*25*24*23*22

= 7893600