644660005 has 16 divisors (see below), whose sum is σ = 852119424. Its totient is φ = 464287680.

The previous prime is 644659979. The next prime is 644660011. The reversal of 644660005 is 500066446.

It is not a de Polignac number, because 644660005 - 2⁷ = 644659877 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51234 + ... + 62563.

It is an arithmetic number, because the mean of its divisors is an integer number (53257464).

Almost surely, 2^644660005 is an apocalyptic number.

It is an amenable number.

644660005 is a deficient number, since it is larger than the sum of its proper divisors (207459419).

644660005 is a wasteful number, since it uses less digits than its factorization.

644660005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113916.

The product of its (nonzero) digits is 17280, while the sum is 31.

The square root of 644660005 is about 25390.1556710470. The cubic root of 644660005 is about 863.8604192134.

The spelling of 644660005 in words is "six hundred forty-four million, six hundred sixty thousand, five".