811999 has 4 divisors (see below), whose sum is σ = 818064. Its totient is φ = 805936.

The previous prime is 811997. The next prime is 812011. The reversal of 811999 is 999118.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 999118 = 2 ⋅499559.

It is a cyclic number.

It is not a de Polignac number, because 811999 - 2¹ = 811997 is a prime.

It is a Duffinian number.

811999 is a modest number, since divided by 999 gives 811 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (811991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2827 + ... + 3100.

It is an arithmetic number, because the mean of its divisors is an integer number (204516).

2⁸¹¹⁹⁹⁹ is an apocalyptic number.

811999 is a deficient number, since it is larger than the sum of its proper divisors (6065).

811999 is a wasteful number, since it uses less digits than its factorization.

811999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6064.

The product of its digits is 5832, while the sum is 37.

The square root of 811999 is about 901.1098712144. The cubic root of 811999 is about 93.2935956120.

It can be divided in two parts, 81 and 1999, that added together give a triangular number (2080 = T₆₄).

The spelling of 811999 in words is "eight hundred eleven thousand, nine hundred ninety-nine".