What are vampire number ?
Inmathematics, avampire number(ortrue vampire number) is acompositenatural numberv, with an even number ofdigitsn, that can be factored into twointegersxandyeach withn/2 digits and not both with trailing zeroes, wherevcontains precisely all the digits fromxand fromy, in any order, counting multiplicity.xandyare called thefangs.
For example: 1260 is a vampire number, with 21 and 60 as fangs, since 21 × 60 = 1260. However, 126000 (which can be expressed as 21 × 6000 or 210 × 600) is not, as 21 and 6000 do not have the correct length, and both 210 and 600 have trailing zeroes. Similarly, 1023 (which can be expressed as 31 × 33) is not, as although 1023 contains all the digits of 31 and 33, the list of digits of the factors does not coincide with the list of digits of the original number.
Inmathematics, avampire number(ortrue vampire number) is acompositenatural numberv, with an even number ofdigitsn, that can be factored into twointegersxandyeach withn/2 digits and not both with trailing zeroes, wherevcontains precisely all the digits fromxand fromy, in any order, counting multiplicity.xandyare called thefangs.
For example: 1260 is a vampire number, with 21 and 60 as fangs, since 21 × 60 = 1260. However, 126000 (which can be expressed as 21 × 6000 or 210 × 600) is not, as 21 and 6000 do not have the correct length, and both 210 and 600 have trailing zeroes. Similarly, 1023 (which can be expressed as 31 × 33) is not, as although 1023 contains all the digits of 31 and 33, the list of digits of the factors does not coincide with the list of digits of the original number.
