813440 has 64 divisors (see below), whose sum is σ = 2056320. Its totient is φ = 307200.

The previous prime is 813427. The next prime is 813443. The reversal of 813440 is 44318.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (813443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19820 + ... + 19860.

It is an arithmetic number, because the mean of its divisors is an integer number (32130).

2⁸¹³⁴⁴⁰ is an apocalyptic number.

813440 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 813440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1028160).

813440 is an abundant number, since it is smaller than the sum of its proper divisors (1242880).

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

813440 is a wasteful number, since it uses less digits than its factorization.

813440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91 (or 79 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 813440 is about 901.9090863274. The cubic root of 813440 is about 93.3487502877.

Adding to 813440 its reverse (44318), we get a palindrome (857758).

The spelling of 813440 in words is "eight hundred thirteen thousand, four hundred forty".