391981888 has 14 divisors (see below), whose sum is σ = 777839186. Its totient is φ = 195990912.

The previous prime is 391981879. The next prime is 391981901. The reversal of 391981888 is 888189193.

It can be written as a sum of positive squares in only one way, i.e., 377602624 + 14379264 = 19432^2 + 3792^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3062295 + ... + 3062422.

Almost surely, 2^391981888 is an apocalyptic number.

It is an amenable number.

391981888 is a deficient number, since it is larger than the sum of its proper divisors (385857298).

391981888 is an equidigital number, since it uses as much as digits as its factorization.

391981888 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6124729 (or 6124719 counting only the distinct ones).

The product of its digits is 995328, while the sum is 55.

The square root of 391981888 is about 19798.5324708676. The cubic root of 391981888 is about 731.8498701737.

The spelling of 391981888 in words is "three hundred ninety-one million, nine hundred eighty-one thousand, eight hundred eighty-eight".