644342881 has 32 divisors (see below), whose sum is σ = 820592640. Its totient is φ = 492388416.

The previous prime is 644342833. The next prime is 644342887. The reversal of 644342881 is 188243446.

It is a happy number.

644342881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644342881 - 2¹⁵ = 644310113 is a prime.

It is a super-2 number, since 2×644342881² = 830355496590760322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644342887) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 336930 + ... + 338836.

It is an arithmetic number, because the mean of its divisors is an integer number (25643520).

Almost surely, 2^644342881 is an apocalyptic number.

It is an amenable number.

644342881 is a deficient number, since it is larger than the sum of its proper divisors (176249759).

644342881 is a wasteful number, since it uses less digits than its factorization.

644342881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2053.

The product of its digits is 147456, while the sum is 40.

The square root of 644342881 is about 25383.9098840190. The cubic root of 644342881 is about 863.7187446341.

The spelling of 644342881 in words is "six hundred forty-four million, three hundred forty-two thousand, eight hundred eighty-one".