813840 has 40 divisors (see below), whose sum is σ = 2523648. Its totient is φ = 216960.

The previous prime is 813833. The next prime is 813847. The reversal of 813840 is 48318.

It is an interprime number because it is at equal distance from previous prime (813833) and next prime (813847).

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 (24).

It is a self number, because there is not a number n which added to its sum of digits gives 813840.

It is not an unprimeable number, because it can be changed into a prime (813847) by changing a digit.

813840 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 7 ways as a sum of consecutive naturals, for example, 1456 + ... + 1935.

2⁸¹³⁸⁴⁰ is an apocalyptic number.

813840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

813840 is an abundant number, since it is smaller than the sum of its proper divisors (1709808).

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

813840 is a wasteful number, since it uses less digits than its factorization.

813840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3407 (or 3401 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 813840 is about 902.1308109138. The cubic root of 813840 is about 93.3640488475.

It can be divided in two parts, 813 and 840, that added together give a triangular number (1653 = T₅₇).

The spelling of 813840 in words is "eight hundred thirteen thousand, eight hundred forty".