644026941565 has 16 divisors (see below), whose sum is σ = 883302417792. Its totient is φ = 441585739584.

The previous prime is 644026941541. The next prime is 644026941587. The reversal of 644026941565 is 565149620446.

It is a cyclic number.

It is not a de Polignac number, because 644026941565 - 2¹³ = 644026933373 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, 198214 + ... + 1152103.

It is an arithmetic number, because the mean of its divisors is an integer number (55206401112).

Almost surely, 2^644026941565 is an apocalyptic number.

It is an amenable number.

644026941565 is a deficient number, since it is larger than the sum of its proper divisors (239275476227).

644026941565 is a wasteful number, since it uses less digits than its factorization.

644026941565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1363956.

The product of its (nonzero) digits is 6220800, while the sum is 52.

The spelling of 644026941565 in words is "six hundred forty-four billion, twenty-six million, nine hundred forty-one thousand, five hundred sixty-five".