391278889 has 4 divisors (see below), whose sum is σ = 391341780. Its totient is φ = 391216000.

The previous prime is 391278883. The next prime is 391278911. The reversal of 391278889 is 988872193.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 265950864 + 125328025 = 16308^2 + 11195^2 .

It is a cyclic number.

It is not a de Polignac number, because 391278889 - 2¹⁷ = 391147817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391278883) 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, 20944 + ... + 34945.

It is an arithmetic number, because the mean of its divisors is an integer number (97835445).

Almost surely, 2^391278889 is an apocalyptic number.

It is an amenable number.

391278889 is a deficient number, since it is larger than the sum of its proper divisors (62891).

391278889 is an equidigital number, since it uses as much as digits as its factorization.

391278889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62890.

The product of its digits is 1741824, while the sum is 55.

The square root of 391278889 is about 19780.7706877159. The cubic root of 391278889 is about 731.4120968823.

The spelling of 391278889 in words is "three hundred ninety-one million, two hundred seventy-eight thousand, eight hundred eighty-nine".