There is only one prime p
such that p!
Find it and prove its uniqueness.
25!=15511210043330985984000000 which is 25 digits long.
p! = p*(p-1)!. Then for p>=10, p! has at least one more digit than (p-1)!.
For p<25, only 23 works: 23! = 25852016738884976640000.
Posted by xdog
on 2016-04-28 09:52:53