644649618 has 16 divisors (see below), whose sum is σ = 1290144960. Its totient is φ = 214742256.

The previous prime is 644649563. The next prime is 644649637. The reversal of 644649618 is 816946446.

It is a happy number.

It is a Curzon number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 25105 + ... + 43812.

It is an arithmetic number, because the mean of its divisors is an integer number (80634060).

Almost surely, 2^644649618 is an apocalyptic number.

644649618 is an abundant number, since it is smaller than the sum of its proper divisors (645495342).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644649618 is a wasteful number, since it uses less digits than its factorization.

644649618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70481.

The product of its digits is 995328, while the sum is 48.

The square root of 644649618 is about 25389.9511224421. The cubic root of 644649618 is about 863.8557795758.

The spelling of 644649618 in words is "six hundred forty-four million, six hundred forty-nine thousand, six hundred eighteen".