400005 has 16 divisors (see below), whose sum is σ = 711360. Its totient is φ = 213264.

The previous prime is 399989. The next prime is 400009. The reversal of 400005 is 500004.

It is not a de Polignac number, because 400005 - 2⁴ = 399989 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 400005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400009) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1347 + ... + 1616.

It is an arithmetic number, because the mean of its divisors is an integer number (44460).

2⁴⁰⁰⁰⁰⁵ is an apocalyptic number.

400005 is a gapful number since it is divisible by the number (45) formed by its first and last digit.

It is an amenable number.

400005 is a deficient number, since it is larger than the sum of its proper divisors (311355).

400005 is a wasteful number, since it uses less digits than its factorization.

400005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2977 (or 2971 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 9.

The square root of 400005 is about 632.4594848684. The cubic root of 400005 is about 73.6809369742.

Adding to 400005 its reverse (500004), we get a palindrome (900009).

Subtracting 400005 from its reverse (500004), we obtain a palindrome (99999).

The spelling of 400005 in words is "four hundred thousand, five".