+128408
1! = 1
1! + 2! = 1 + 2 = 3
1! + 2! + 3! = 3 + 6 = 9
1! + 2! + 3! + 4! = 9 + 24 = 33
1 + 2! + 3! + 4! + 5! = 33 + 120 = 153
Note that every successive factorial added to his sum will include 2 and 5 as multipliers...so every successive factorial will end in 0.....so
1! + 2! + 3! + 4! + 5! .....+ 1000! will have a units digits sum of 3
Thanks in advance.
