405981 has 12 divisors (see below), whose sum is σ = 594880. Its totient is φ = 266760.

The previous prime is 405967. The next prime is 405989. The reversal of 405981 is 189504.

It is not a de Polignac number, because 405981 - 2⁵ = 405949 is a prime.

It is a super-2 number, since 2×405981² = 329641144722, which contains 22 as substring.

It is a Duffinian 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 405981.

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

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 426 + ... + 996.

2⁴⁰⁵⁹⁸¹ is an apocalyptic number.

It is an amenable number.

405981 is a deficient number, since it is larger than the sum of its proper divisors (188899).

405981 is a wasteful number, since it uses less digits than its factorization.

405981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 656 (or 653 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 405981 is about 637.1663832940. The cubic root of 405981 is about 74.0460511994.

The spelling of 405981 in words is "four hundred five thousand, nine hundred eighty-one".