844640821 has 4 divisors (see below), whose sum is σ = 848428672. Its totient is φ = 840852972.

The previous prime is 844640813. The next prime is 844640827. The reversal of 844640821 is 128046448.

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 844640821 - 2³ = 844640813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (844640827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1893591 + ... + 1894036.

It is an arithmetic number, because the mean of its divisors is an integer number (212107168).

Almost surely, 2^844640821 is an apocalyptic number.

It is an amenable number.

844640821 is a deficient number, since it is larger than the sum of its proper divisors (3787851).

844640821 is a wasteful number, since it uses less digits than its factorization.

844640821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3787850.

The product of its (nonzero) digits is 49152, while the sum is 37.

The square root of 844640821 is about 29062.7049842233. The cubic root of 844640821 is about 945.2732227895.

The spelling of 844640821 in words is "eight hundred forty-four million, six hundred forty thousand, eight hundred twenty-one".