820581 has 4 divisors (see below), whose sum is σ = 1094112. Its totient is φ = 547052.

The previous prime is 820577. The next prime is 820597. The reversal of 820581 is 185028.

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 820581 - 2² = 820577 is a prime.

It is a super-2 number, since 2×820581² = 1346706355122, which contains 22 as substring.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820541) 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, 136761 + ... + 136766.

It is an arithmetic number, because the mean of its divisors is an integer number (273528).

2⁸²⁰⁵⁸¹ is an apocalyptic number.

It is an amenable number.

820581 is a deficient number, since it is larger than the sum of its proper divisors (273531).

820581 is a wasteful number, since it uses less digits than its factorization.

820581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 273530.

The product of its (nonzero) digits is 640, while the sum is 24.

The square root of 820581 is about 905.8592605918. The cubic root of 820581 is about 93.6211171216.

The spelling of 820581 in words is "eight hundred twenty thousand, five hundred eighty-one".