391391861 has 6 divisors (see below), whose sum is σ = 455292630. Its totient is φ = 335478696.

The previous prime is 391391857. The next prime is 391391873. The reversal of 391391861 is 168193193.

It can be written as a sum of positive squares in only one way, i.e., 228191236 + 163200625 = 15106^2 + 12775^2 .

It is not a de Polignac number, because 391391861 - 2² = 391391857 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 (391391761) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3993746 + ... + 3993843.

It is an arithmetic number, because the mean of its divisors is an integer number (75882105).

Almost surely, 2^391391861 is an apocalyptic number.

It is an amenable number.

391391861 is a deficient number, since it is larger than the sum of its proper divisors (63900769).

391391861 is an equidigital number, since it uses as much as digits as its factorization.

391391861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7987603 (or 7987596 counting only the distinct ones).

The product of its digits is 34992, while the sum is 41.

The square root of 391391861 is about 19783.6260832033. The cubic root of 391391861 is about 731.4824824296.

The spelling of 391391861 in words is "three hundred ninety-one million, three hundred ninety-one thousand, eight hundred sixty-one".