400405 has 8 divisors (see below), whose sum is σ = 487512. Its totient is φ = 315648.

The previous prime is 400391. The next prime is 400409. The reversal of 400405 is 504004.

400405 = 35² + 36² + ... + 107².

It can be written as a sum of positive squares in 4 ways, for example, as 23409 + 376996 = 153^2 + 614^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 400405 - 2⁷ = 400277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400409) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 184 + ... + 913.

It is an arithmetic number, because the mean of its divisors is an integer number (60939).

2⁴⁰⁰⁴⁰⁵ is an apocalyptic number.

It is an amenable number.

400405 is a deficient number, since it is larger than the sum of its proper divisors (87107).

400405 is a wasteful number, since it uses less digits than its factorization.

400405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1175.

The product of its (nonzero) digits is 80, while the sum is 13.

The square root of 400405 is about 632.7756316421. The cubic root of 400405 is about 73.7054887975.

Adding to 400405 its reverse (504004), we get a palindrome (904409).

The spelling of 400405 in words is "four hundred thousand, four hundred five".