872821 has 4 divisors (see below), whose sum is σ = 874732. Its totient is φ = 870912.

The previous prime is 872791. The next prime is 872843. The reversal of 872821 is 128278.

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 617796 + 255025 = 786^2 + 505^2 .

It is a cyclic number.

It is not a de Polignac number, because 872821 - 2⁵ = 872789 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 872821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (872621) 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, 181 + ... + 1333.

It is an arithmetic number, because the mean of its divisors is an integer number (218683).

2⁸⁷²⁸²¹ is an apocalyptic number.

It is an amenable number.

872821 is a deficient number, since it is larger than the sum of its proper divisors (1911).

872821 is a wasteful number, since it uses less digits than its factorization.

872821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1910.

The product of its digits is 1792, while the sum is 28.

The square root of 872821 is about 934.2488961727. The cubic root of 872821 is about 95.5670973880.

The spelling of 872821 in words is "eight hundred seventy-two thousand, eight hundred twenty-one".