644287663 has 16 divisors (see below), whose sum is σ = 713318400. Its totient is φ = 579515040.

The previous prime is 644287621. The next prime is 644287667. The reversal of 644287663 is 366782446.

It is a cyclic number.

It is not a de Polignac number, because 644287663 - 2⁹ = 644287151 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644287667) 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, 20898 + ... + 41536.

It is an arithmetic number, because the mean of its divisors is an integer number (44582400).

Almost surely, 2^644287663 is an apocalyptic number.

644287663 is a deficient number, since it is larger than the sum of its proper divisors (69030737).

644287663 is a wasteful number, since it uses less digits than its factorization.

644287663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20742.

The product of its digits is 1161216, while the sum is 46.

The square root of 644287663 is about 25382.8222032145. The cubic root of 644287663 is about 863.6940713401.

The spelling of 644287663 in words is "six hundred forty-four million, two hundred eighty-seven thousand, six hundred sixty-three".