391440 has 80 divisors (see below), whose sum is σ = 1392768. Its totient is φ = 89088.

The previous prime is 391403. The next prime is 391441. The reversal of 391440 is 44193.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 391440.

It is not an unprimeable number, because it can be changed into a prime (391441) by changing a digit.

391440 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1564 + ... + 1796.

2³⁹¹⁴⁴⁰ is an apocalyptic number.

391440 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 391440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (696384).

391440 is an abundant number, since it is smaller than the sum of its proper divisors (1001328).

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

391440 is a wasteful number, since it uses less digits than its factorization.

391440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256 (or 250 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 391440 is about 625.6516602711. The cubic root of 391440 is about 73.1512470612.

The spelling of 391440 in words is "three hundred ninety-one thousand, four hundred forty".