821644427 has 4 divisors (see below), whose sum is σ = 822373320. Its totient is φ = 820915536.

The previous prime is 821644423. The next prime is 821644451. The reversal of 821644427 is 724446128.

821644427 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 is a cyclic number.

It is not a de Polignac number, because 821644427 - 2² = 821644423 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821644423) 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, 362753 + ... + 365010.

It is an arithmetic number, because the mean of its divisors is an integer number (205593330).

Almost surely, 2^821644427 is an apocalyptic number.

821644427 is a deficient number, since it is larger than the sum of its proper divisors (728893).

821644427 is a wasteful number, since it uses less digits than its factorization.

821644427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 728892.

The product of its digits is 86016, while the sum is 38.

The square root of 821644427 is about 28664.3406866441. The cubic root of 821644427 is about 936.6154223783.

The spelling of 821644427 in words is "eight hundred twenty-one million, six hundred forty-four thousand, four hundred twenty-seven".