8391440 has 40 divisors (see below), whose sum is σ = 20188440. Its totient is φ = 3239936.

The previous prime is 8391433. The next prime is 8391443. The reversal of 8391440 is 441938.

It can be written as a sum of positive squares in 4 ways, for example, as 4624 + 8386816 = 68^2 + 2896^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (29).

It is not an unprimeable number, because it can be changed into a prime (8391443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 512 + ... + 4128.

It is an arithmetic number, because the mean of its divisors is an integer number (504711).

Almost surely, 2^8391440 is an apocalyptic number.

8391440 is a gapful number since it is divisible by the number (80) 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 8391440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (10094220).

8391440 is an abundant number, since it is smaller than the sum of its proper divisors (11797000).

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

8391440 is a wasteful number, since it uses less digits than its factorization.

8391440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3659 (or 3653 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 8391440 is about 2896.7982325319. The cubic root of 8391440 is about 203.2101974753.

The spelling of 8391440 in words is "eight million, three hundred ninety-one thousand, four hundred forty".