644072365 has 4 divisors (see below), whose sum is σ = 772886844. Its totient is φ = 515257888.

The previous prime is 644072329. The next prime is 644072383. The reversal of 644072365 is 563270446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 563270446 = 2 ⋅281635223.

It can be written as a sum of positive squares in 2 ways, for example, as 187224489 + 456847876 = 13683^2 + 21374^2 .

It is a cyclic number.

It is not a de Polignac number, because 644072365 - 2⁷ = 644072237 is a prime.

It is a super-2 number, since 2×644072365² = 829658422713386450, which contains 22 as substring.

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 3 ways as a sum of consecutive naturals, for example, 64407232 + ... + 64407241.

It is an arithmetic number, because the mean of its divisors is an integer number (193221711).

Almost surely, 2^644072365 is an apocalyptic number.

It is an amenable number.

644072365 is a deficient number, since it is larger than the sum of its proper divisors (128814479).

644072365 is a wasteful number, since it uses less digits than its factorization.

644072365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128814478.

The product of its (nonzero) digits is 120960, while the sum is 37.

The square root of 644072365 is about 25378.5808310867. The cubic root of 644072365 is about 863.5978553517.

The spelling of 644072365 in words is "six hundred forty-four million, seventy-two thousand, three hundred sixty-five".