Q: Is 400,409 a Prime Number?
A: Yes, 400,409 is a prime number.
A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 400409 can be evenly divided by 1 and 400,409, with no remainder.
Since 400,409 can be divided by just 1 and 400,409, it is a prime number.