391978340 has 24 divisors (see below), whose sum is σ = 886474680. Its totient is φ = 144730368.

The previous prime is 391978309. The next prime is 391978369. The reversal of 391978340 is 43879193.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4990756 + 386987584 = 2234^2 + 19672^2 .

It is a junction number, because it is equal to n+sod(n) for n = 391978291 and 391978300.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 753545 + ... + 754064.

It is an arithmetic number, because the mean of its divisors is an integer number (36936445).

Almost surely, 2^391978340 is an apocalyptic number.

It is an amenable number.

391978340 is an abundant number, since it is smaller than the sum of its proper divisors (494496340).

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

391978340 is a wasteful number, since it uses less digits than its factorization.

391978340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1507631 (or 1507629 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 44.

The square root of 391978340 is about 19798.4428680641. The cubic root of 391978340 is about 731.8476620690.

The spelling of 391978340 in words is "three hundred ninety-one million, nine hundred seventy-eight thousand, three hundred forty".