820565 has 4 divisors (see below), whose sum is σ = 984684. Its totient is φ = 656448.

The previous prime is 820559. The next prime is 820577. The reversal of 820565 is 565028.

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 401956 + 418609 = 634^2 + 647^2 .

It is a cyclic number.

It is not a de Polignac number, because 820565 - 2¹² = 816469 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82052 + ... + 82061.

It is an arithmetic number, because the mean of its divisors is an integer number (246171).

2⁸²⁰⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

820565 is a deficient number, since it is larger than the sum of its proper divisors (164119).

820565 is a wasteful number, since it uses less digits than its factorization.

820565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164118.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 820565 is about 905.8504291548. The cubic root of 820565 is about 93.6205086309.

The spelling of 820565 in words is "eight hundred twenty thousand, five hundred sixty-five".