819985 has 4 divisors (see below), whose sum is σ = 983988. Its totient is φ = 655984.

The previous prime is 819977. The next prime is 819989. The reversal of 819985 is 589918.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 192721 + 627264 = 439^2 + 792^2 .

It is a cyclic number.

It is not a de Polignac number, because 819985 - 2³ = 819977 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (819989) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 81994 + ... + 82003.

It is an arithmetic number, because the mean of its divisors is an integer number (245997).

2⁸¹⁹⁹⁸⁵ is an apocalyptic number.

It is an amenable number.

819985 is a deficient number, since it is larger than the sum of its proper divisors (164003).

819985 is a wasteful number, since it uses less digits than its factorization.

819985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164002.

The product of its digits is 25920, while the sum is 40.

The square root of 819985 is about 905.5302314114. The cubic root of 819985 is about 93.5984455022.

The spelling of 819985 in words is "eight hundred nineteen thousand, nine hundred eighty-five".