644164863 has 16 divisors (see below), whose sum is σ = 864465120. Its totient is φ = 426662784.

The previous prime is 644164861. The next prime is 644164919. The reversal of 644164863 is 368461446.

It is a happy number.

It is not a de Polignac number, because 644164863 - 2¹ = 644164861 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644164861) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 530445 + ... + 531657.

It is an arithmetic number, because the mean of its divisors is an integer number (54029070).

Almost surely, 2^644164863 is an apocalyptic number.

644164863 is a deficient number, since it is larger than the sum of its proper divisors (220300257).

644164863 is a wasteful number, since it uses less digits than its factorization.

644164863 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2218.

The product of its digits is 331776, while the sum is 42.

The square root of 644164863 is about 25380.4031291861. The cubic root of 644164863 is about 863.6391950392.

The spelling of 644164863 in words is "six hundred forty-four million, one hundred sixty-four thousand, eight hundred sixty-three".