391517988 has 12 divisors (see below), whose sum is σ = 913542000. Its totient is φ = 130505992.

The previous prime is 391517969. The next prime is 391518011. The reversal of 391517988 is 889715193.

It is a tau number, because it is divible by the number of its divisors (12).

It is a self number, because there is not a number n which added to its sum of digits gives 391517988.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16313238 + ... + 16313261.

It is an arithmetic number, because the mean of its divisors is an integer number (76128500).

Almost surely, 2^391517988 is an apocalyptic number.

It is an amenable number.

391517988 is an abundant number, since it is smaller than the sum of its proper divisors (522024012).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

391517988 is a wasteful number, since it uses less digits than its factorization.

391517988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32626506 (or 32626504 counting only the distinct ones).

The product of its digits is 544320, while the sum is 51.

The square root of 391517988 is about 19786.8134877751. The cubic root of 391517988 is about 731.5610480069.

The spelling of 391517988 in words is "three hundred ninety-one million, five hundred seventeen thousand, nine hundred eighty-eight".