391897988 has 6 divisors (see below), whose sum is σ = 685821486. Its totient is φ = 195948992.

The previous prime is 391897973. The next prime is 391898011. The reversal of 391897988 is 889798193.

It can be written as a sum of positive squares in only one way, i.e., 391723264 + 174724 = 19792^2 + 418^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 391897988.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 48987245 + ... + 48987252.

It is an arithmetic number, because the mean of its divisors is an integer number (114303581).

Almost surely, 2^391897988 is an apocalyptic number.

It is an amenable number.

391897988 is a deficient number, since it is larger than the sum of its proper divisors (293923498).

391897988 is a wasteful number, since it uses less digits than its factorization.

391897988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97974501 (or 97974499 counting only the distinct ones).

The product of its digits is 7838208, while the sum is 62.

The square root of 391897988 is about 19796.4135135635. The cubic root of 391897988 is about 731.7976512767.

The spelling of 391897988 in words is "three hundred ninety-one million, eight hundred ninety-seven thousand, nine hundred eighty-eight".