644885863 has 2 divisors, whose sum is σ = 644885864. Its totient is φ = 644885862.

The previous prime is 644885809. The next prime is 644885881. The reversal of 644885863 is 368588446.

644885863 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644885863 - 2¹³ = 644877671 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644885863.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644886863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322442931 + 322442932.

It is an arithmetic number, because the mean of its divisors is an integer number (322442932).

Almost surely, 2^644885863 is an apocalyptic number.

644885863 is a deficient number, since it is larger than the sum of its proper divisors (1).

644885863 is an equidigital number, since it uses as much as digits as its factorization.

644885863 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4423680, while the sum is 52.

The square root of 644885863 is about 25394.6030289902. The cubic root of 644885863 is about 863.9612925439.

The spelling of 644885863 in words is "six hundred forty-four million, eight hundred eighty-five thousand, eight hundred sixty-three".