391981889 has 8 divisors (see below), whose sum is σ = 422461032. Its totient is φ = 361549440.

The previous prime is 391981879. The next prime is 391981901. The reversal of 391981889 is 988189193.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 158961664 + 233020225 = 12608^2 + 15265^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 391981889 - 2⁸ = 391981633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391981879) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6869 + ... + 28829.

It is an arithmetic number, because the mean of its divisors is an integer number (52807629).

Almost surely, 2^391981889 is an apocalyptic number.

It is an amenable number.

391981889 is a deficient number, since it is larger than the sum of its proper divisors (30479143).

391981889 is a wasteful number, since it uses less digits than its factorization.

391981889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23347.

The product of its digits is 1119744, while the sum is 56.

The square root of 391981889 is about 19798.5324961220. The cubic root of 391981889 is about 731.8498707960.

The spelling of 391981889 in words is "three hundred ninety-one million, nine hundred eighty-one thousand, eight hundred eighty-nine".