816809 has 4 divisors (see below), whose sum is σ = 933504. Its totient is φ = 700116.

The previous prime is 816779. The next prime is 816811. The reversal of 816809 is 908618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 816809 - 2¹⁶ = 751273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (816839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 58337 + ... + 58350.

It is an arithmetic number, because the mean of its divisors is an integer number (233376).

2⁸¹⁶⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

816809 is a deficient number, since it is larger than the sum of its proper divisors (116695).

816809 is a wasteful number, since it uses less digits than its factorization.

816809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116694.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 816809 is about 903.7748613455. The cubic root of 816809 is about 93.4774460170.

Subtracting 816809 from its reverse (908618), we obtain a square (91809 = 303²).

The spelling of 816809 in words is "eight hundred sixteen thousand, eight hundred nine".