644333865 has 64 divisors (see below), whose sum is σ = 1198325760. Its totient is φ = 289578240.

The previous prime is 644333863. The next prime is 644333869. The reversal of 644333865 is 568333446.

It is not a de Polignac number, because 644333865 - 2¹ = 644333863 is a prime.

It is a super-2 number, since 2×644333865² = 830332259171676450, which contains 22 as substring.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (644333863) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2813571 + ... + 2813799.

It is an arithmetic number, because the mean of its divisors is an integer number (18723840).

Almost surely, 2^644333865 is an apocalyptic number.

It is an amenable number.

644333865 is a deficient number, since it is larger than the sum of its proper divisors (553991895).

644333865 is a wasteful number, since it uses less digits than its factorization.

644333865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 582.

The product of its digits is 622080, while the sum is 42.

The square root of 644333865 is about 25383.7322905833. The cubic root of 644333865 is about 863.7147160727.

The spelling of 644333865 in words is "six hundred forty-four million, three hundred thirty-three thousand, eight hundred sixty-five".