811840 has 56 divisors (see below), whose sum is σ = 2011680. Its totient is φ = 311808.

The previous prime is 811819. The next prime is 811861. The reversal of 811840 is 48118.

It is an interprime number because it is at equal distance from previous prime (811819) and next prime (811861).

It is a congruent number.

It is an unprimeable number.

811840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 13731 + ... + 13789.

2⁸¹¹⁸⁴⁰ is an apocalyptic number.

811840 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 811840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1005840).

811840 is an abundant number, since it is smaller than the sum of its proper divisors (1199840).

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

811840 is a wasteful number, since it uses less digits than its factorization.

811840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119 (or 109 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 22.

The square root of 811840 is about 901.0216423594. The cubic root of 811840 is about 93.2875058467.

Adding to 811840 its reverse (48118), we get a palindrome (859958).

The spelling of 811840 in words is "eight hundred eleven thousand, eight hundred forty".