405921 has 8 divisors (see below), whose sum is σ = 544320. Its totient is φ = 269072.

The previous prime is 405917. The next prime is 405947. The reversal of 405921 is 129504.

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 405921 - 2² = 405917 is a prime.

405921 is a lucky number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 405921.

It is not an unprimeable number, because it can be changed into a prime (405901) 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, 556 + ... + 1058.

It is an arithmetic number, because the mean of its divisors is an integer number (68040).

2⁴⁰⁵⁹²¹ is an apocalyptic number.

It is an amenable number.

405921 is a deficient number, since it is larger than the sum of its proper divisors (138399).

405921 is a wasteful number, since it uses less digits than its factorization.

405921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 775.

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 405921 is about 637.1192980910. The cubic root of 405921 is about 74.0424032603.

It can be divided in two parts, 405 and 921, that added together give a triangular number (1326 = T₅₁).

The spelling of 405921 in words is "four hundred five thousand, nine hundred twenty-one".