405985 has 4 divisors (see below), whose sum is σ = 487188. Its totient is φ = 324784.

The previous prime is 405967. The next prime is 405989. The reversal of 405985 is 589504.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 197136 + 208849 = 444^2 + 457^2 .

It is a cyclic number.

It is not a de Polignac number, because 405985 - 2⁷ = 405857 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

405985 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (405989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40594 + ... + 40603.

It is an arithmetic number, because the mean of its divisors is an integer number (121797).

2⁴⁰⁵⁹⁸⁵ is an apocalyptic number.

It is an amenable number.

405985 is a deficient number, since it is larger than the sum of its proper divisors (81203).

405985 is an equidigital number, since it uses as much as digits as its factorization.

405985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81202.

The product of its (nonzero) digits is 7200, while the sum is 31.

The square root of 405985 is about 637.1695221839. The cubic root of 405985 is about 74.0462943826.

The spelling of 405985 in words is "four hundred five thousand, nine hundred eighty-five".