405581 has 4 divisors (see below), whose sum is σ = 442464. Its totient is φ = 368700.

The previous prime is 405577. The next prime is 405599. The reversal of 405581 is 185504.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 405581 - 2² = 405577 is a prime.

It is a super-2 number, since 2×405581² = 328991895122, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 405581.

It is not an unprimeable number, because it can be changed into a prime (405521) 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, 18425 + ... + 18446.

It is an arithmetic number, because the mean of its divisors is an integer number (110616).

2⁴⁰⁵⁵⁸¹ is an apocalyptic number.

It is an amenable number.

405581 is a deficient number, since it is larger than the sum of its proper divisors (36883).

405581 is a wasteful number, since it uses less digits than its factorization.

405581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36882.

The product of its (nonzero) digits is 800, while the sum is 23.

The square root of 405581 is about 636.8524161845. The cubic root of 405581 is about 74.0217248121.

It can be divided in two parts, 4055 and 81, that multiplied together give a triangular number (328455 = T₈₁₀).

The spelling of 405581 in words is "four hundred five thousand, five hundred eighty-one".