812809 has 4 divisors (see below), whose sum is σ = 820116. Its totient is φ = 805504.

The previous prime is 812807. The next prime is 812849. The reversal of 812809 is 908218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 908218 = 2 ⋅454109.

It can be written as a sum of positive squares in 2 ways, for example, as 29584 + 783225 = 172^2 + 885^2 .

It is a cyclic number.

It is not a de Polignac number, because 812809 - 2¹ = 812807 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (812807) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3484 + ... + 3709.

It is an arithmetic number, because the mean of its divisors is an integer number (205029).

2⁸¹²⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

812809 is a deficient number, since it is larger than the sum of its proper divisors (7307).

812809 is a wasteful number, since it uses less digits than its factorization.

812809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7306.

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 812809 is about 901.5592049333. The cubic root of 812809 is about 93.3246066104.

It can be divided in two parts, 81 and 2809, that multiplied together give a square (227529 = 477²).

The spelling of 812809 in words is "eight hundred twelve thousand, eight hundred nine".