Which is the biggest Prime number less than 9999??
Number Theory
Level
2
Find the unit digit of sum of factorials of all prime numbers less than the biggest 4 digit number.
The answer is 8.
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1 solution
The series will be something like this.. 2! + 3! + 5! + 7! ............ Since in all factorials after 5 the unit digit is 0 So the unit digit in the entire sum will be the unit digit of 2!+3! i.e. 8