391309 has 4 divisors (see below), whose sum is σ = 393120. Its totient is φ = 389500.

The previous prime is 391301. The next prime is 391331. The reversal of 391309 is 903193.

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, and also an emirpimes, since its reverse is a distinct semiprime: 903193 = 17 ⋅53129.

It is a cyclic number.

It is not a de Polignac number, because 391309 - 2³ = 391301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391301) 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, 529 + ... + 1030.

It is an arithmetic number, because the mean of its divisors is an integer number (98280).

2³⁹¹³⁰⁹ is an apocalyptic number.

It is an amenable number.

391309 is a deficient number, since it is larger than the sum of its proper divisors (1811).

391309 is a wasteful number, since it uses less digits than its factorization.

391309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1810.

The product of its (nonzero) digits is 729, while the sum is 25.

The square root of 391309 is about 625.5469606672. The cubic root of 391309 is about 73.1430858423.

The spelling of 391309 in words is "three hundred ninety-one thousand, three hundred nine".