A factorion is a natural number that equals the sum of the factorials of its decimal digits. For example, 145 is a factorion because 1! + 4! + 5! = 1 + 24 + 120 = 145.
There are just four factorions (in base 10) and they are 1, 2, 145 and 40585
~Text is copied from Wiki~
What they can ask :
There are how many natural number(s) which is(are) equal to summation of factorials of all its digits.
So remember answer is 4 and numbers are 1, 2, 145 and 40585.
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