391312891 has 4 divisors (see below), whose sum is σ = 391594000. Its totient is φ = 391031784.

The previous prime is 391312877. The next prime is 391312937. The reversal of 391312891 is 198213193.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 198213193 = 173 ⋅1145741.

It is a cyclic number.

It is not a de Polignac number, because 391312891 - 2¹³ = 391304699 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 391312891.

It is not an unprimeable number, because it can be changed into a prime (391312811) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 138456 + ... + 141253.

It is an arithmetic number, because the mean of its divisors is an integer number (97898500).

Almost surely, 2^391312891 is an apocalyptic number.

391312891 is a deficient number, since it is larger than the sum of its proper divisors (281109).

391312891 is a wasteful number, since it uses less digits than its factorization.

391312891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281108.

The product of its digits is 11664, while the sum is 37.

The square root of 391312891 is about 19781.6301401073. The cubic root of 391312891 is about 731.4332827546.

The spelling of 391312891 in words is "three hundred ninety-one million, three hundred twelve thousand, eight hundred ninety-one".