391989924 has 18 divisors (see below), whose sum is σ = 990863510. Its totient is φ = 130663296.

The previous prime is 391989919. The next prime is 391989937. The reversal of 391989924 is 429989193.

It can be written as a sum of positive squares in only one way, i.e., 262440000 + 129549924 = 16200^2 + 11382^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×391989924² = 307312201035051552, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5444269 + ... + 5444340.

Almost surely, 2^391989924 is an apocalyptic number.

It is an amenable number.

391989924 is an abundant number, since it is smaller than the sum of its proper divisors (598873586).

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

391989924 is a wasteful number, since it uses less digits than its factorization.

391989924 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10888619 (or 10888614 counting only the distinct ones).

The product of its digits is 1259712, while the sum is 54.

The square root of 391989924 is about 19798.7354141622. The cubic root of 391989924 is about 731.8548713447.

The spelling of 391989924 in words is "three hundred ninety-one million, nine hundred eighty-nine thousand, nine hundred twenty-four".