391568640 has 144 divisors (see below), whose sum is σ = 1263584448. Its totient is φ = 103333888.

The previous prime is 391568603. The next prime is 391568641. The reversal of 391568640 is 46865193.

It is a junction number, because it is equal to n+sod(n) for n = 391568592 and 391568601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391568641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 410404 + ... + 411356.

It is an arithmetic number, because the mean of its divisors is an integer number (8774892).

Almost surely, 2^391568640 is an apocalyptic number.

391568640 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 391568640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (631792224).

391568640 is an abundant number, since it is smaller than the sum of its proper divisors (872015808).

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

391568640 is a wasteful number, since it uses less digits than its factorization.

391568640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1084 (or 1070 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 42.

The square root of 391568640 is about 19788.0933897129. The cubic root of 391568640 is about 731.5925948183.

The spelling of 391568640 in words is "three hundred ninety-one million, five hundred sixty-eight thousand, six hundred forty".