805821 has 4 divisors (see below), whose sum is σ = 1074432. Its totient is φ = 537212.

The previous prime is 805811. The next prime is 805843. The reversal of 805821 is 128508.

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 805821 - 2⁵ = 805789 is a prime.

It is a D-number.

It is a junction number, because it is equal to n+sod(n) for n = 805791 and 805800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (805811) 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, 134301 + ... + 134306.

It is an arithmetic number, because the mean of its divisors is an integer number (268608).

2⁸⁰⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

805821 is a deficient number, since it is larger than the sum of its proper divisors (268611).

805821 is a wasteful number, since it uses less digits than its factorization.

805821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268610.

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

The square root of 805821 is about 897.6753310635. The cubic root of 805821 is about 93.0563885110.

The spelling of 805821 in words is "eight hundred five thousand, eight hundred twenty-one".