390921 has 4 divisors (see below), whose sum is σ = 521232. Its totient is φ = 260612.

The previous prime is 390893. The next prime is 390953. The reversal of 390921 is 129093.

It is a happy number.

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 390921 - 2⁵ = 390889 is a prime.

It is a D-number.

390921 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 390891 and 390900.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 390921.

It is not an unprimeable number, because it can be changed into a prime (390961) 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 3 ways as a sum of consecutive naturals, for example, 65151 + ... + 65156.

It is an arithmetic number, because the mean of its divisors is an integer number (130308).

2³⁹⁰⁹²¹ is an apocalyptic number.

It is an amenable number.

390921 is a deficient number, since it is larger than the sum of its proper divisors (130311).

390921 is a wasteful number, since it uses less digits than its factorization.

390921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130310.

The product of its (nonzero) digits is 486, while the sum is 24.

The square root of 390921 is about 625.2367551576. The cubic root of 390921 is about 73.1189029908.

It can be divided in two parts, 39092 and 1, that added together give a palindrome (39093).

The spelling of 390921 in words is "three hundred ninety thousand, nine hundred twenty-one".