2805821 has 4 divisors (see below), whose sum is σ = 2881692. Its totient is φ = 2729952.

The previous prime is 2805809. The next prime is 2805827. The reversal of 2805821 is 1285082.

2805821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 2524921 + 280900 = 1589^2 + 530^2 .

It is a cyclic number.

It is not a de Polignac number, because 2805821 - 2⁶ = 2805757 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2805827) 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, 37880 + ... + 37953.

It is an arithmetic number, because the mean of its divisors is an integer number (720423).

2^2805821 is an apocalyptic number.

It is an amenable number.

2805821 is a deficient number, since it is larger than the sum of its proper divisors (75871).

2805821 is an equidigital number, since it uses as much as digits as its factorization.

2805821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75870.

The product of its (nonzero) digits is 1280, while the sum is 26.

The square root of 2805821 is about 1675.0585064409. The cubic root of 2805821 is about 141.0435792394.

The spelling of 2805821 in words is "two million, eight hundred five thousand, eight hundred twenty-one".