391909 has 4 divisors (see below), whose sum is σ = 447904. Its totient is φ = 335916.

The previous prime is 391907. The next prime is 391921. The reversal of 391909 is 909193.

391909 is nontrivially palindromic in base 6.

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: 909193 = 127 ⋅7159.

It is not a de Polignac number, because 391909 - 2¹ = 391907 is a prime.

It is a Duffinian number.

391909 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27987 + ... + 28000.

It is an arithmetic number, because the mean of its divisors is an integer number (111976).

2³⁹¹⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

391909 is a deficient number, since it is larger than the sum of its proper divisors (55995).

391909 is an equidigital number, since it uses as much as digits as its factorization.

391909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55994.

The product of its (nonzero) digits is 2187, while the sum is 31.

The square root of 391909 is about 626.0263572726. The cubic root of 391909 is about 73.1804505510.

The spelling of 391909 in words is "three hundred ninety-one thousand, nine hundred nine".