644105665 has 16 divisors (see below), whose sum is σ = 883907712. Its totient is φ = 441391104.

The previous prime is 644105663. The next prime is 644105669. The reversal of 644105665 is 566501446.

644105665 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644105665 - 2¹ = 644105663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644105663) 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, 60417 + ... + 70273.

It is an arithmetic number, because the mean of its divisors is an integer number (55244232).

Almost surely, 2^644105665 is an apocalyptic number.

It is an amenable number.

644105665 is a deficient number, since it is larger than the sum of its proper divisors (239802047).

644105665 is a wasteful number, since it uses less digits than its factorization.

644105665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11736.

The product of its (nonzero) digits is 86400, while the sum is 37.

The square root of 644105665 is about 25379.2368876607. The cubic root of 644105665 is about 863.6127384169.

The spelling of 644105665 in words is "six hundred forty-four million, one hundred five thousand, six hundred sixty-five".