644819538017 has 4 divisors (see below), whose sum is σ = 644854237380. Its totient is φ = 644784838656.

The previous prime is 644819537993. The next prime is 644819538023. The reversal of 644819538017 is 710835918446.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 710835918446 = 2 ⋅355417959223.

It can be written as a sum of positive squares in 2 ways, for example, as 402515382481 + 242304155536 = 634441^2 + 492244^2 .

It is a cyclic number.

It is not a de Polignac number, because 644819538017 - 2¹⁸ = 644819275873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644819538317) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17321792 + ... + 17358977.

It is an arithmetic number, because the mean of its divisors is an integer number (161213559345).

Almost surely, 2^644819538017 is an apocalyptic number.

It is an amenable number.

644819538017 is a deficient number, since it is larger than the sum of its proper divisors (34699363).

644819538017 is a wasteful number, since it uses less digits than its factorization.

644819538017 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34699362.

The product of its (nonzero) digits is 5806080, while the sum is 56.

The spelling of 644819538017 in words is "six hundred forty-four billion, eight hundred nineteen million, five hundred thirty-eight thousand, seventeen".