391475981 has 12 divisors (see below), whose sum is σ = 444951612. Its totient is φ = 342339264.

The previous prime is 391475971. The next prime is 391476013. The reversal of 391475981 is 189574193.

It can be written as a sum of positive squares in 2 ways, for example, as 40513225 + 350962756 = 6365^2 + 18734^2 .

It is not a de Polignac number, because 391475981 - 2²² = 387281677 is a prime.

It is a super-2 number, since 2×391475981² = 306506887399824722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391475921) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 37016 + ... + 46401.

It is an arithmetic number, because the mean of its divisors is an integer number (37079301).

Almost surely, 2^391475981 is an apocalyptic number.

It is an amenable number.

391475981 is a deficient number, since it is larger than the sum of its proper divisors (53475631).

391475981 is a wasteful number, since it uses less digits than its factorization.

391475981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83468 (or 83449 counting only the distinct ones).

The product of its digits is 272160, while the sum is 47.

The square root of 391475981 is about 19785.7519695361. The cubic root of 391475981 is about 731.5348833649.

The spelling of 391475981 in words is "three hundred ninety-one million, four hundred seventy-five thousand, nine hundred eighty-one".