644460653 has 4 divisors (see below), whose sum is σ = 646968540. Its totient is φ = 641952768.

The previous prime is 644460629. The next prime is 644460689. The reversal of 644460653 is 356064446.

It is a happy number.

644460653 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 560884489 + 83576164 = 23683^2 + 9142^2 .

It is a cyclic number.

It is not a de Polignac number, because 644460653 - 2¹² = 644456557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644460623) 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, 1253558 + ... + 1254071.

It is an arithmetic number, because the mean of its divisors is an integer number (161742135).

Almost surely, 2^644460653 is an apocalyptic number.

It is an amenable number.

644460653 is a deficient number, since it is larger than the sum of its proper divisors (2507887).

644460653 is a wasteful number, since it uses less digits than its factorization.

644460653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2507886.

The product of its (nonzero) digits is 207360, while the sum is 38.

The square root of 644460653 is about 25386.2295940142. The cubic root of 644460653 is about 863.7713644892.

The spelling of 644460653 in words is "six hundred forty-four million, four hundred sixty thousand, six hundred fifty-three".