644919870 has 48 divisors (see below), whose sum is σ = 1800515088. Its totient is φ = 147409920.

The previous prime is 644919859. The next prime is 644919881. The reversal of 644919870 is 78919446.

644919870 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (644919859) and next prime (644919881).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 217891 + ... + 220830.

It is an arithmetic number, because the mean of its divisors is an integer number (37510731).

Almost surely, 2^644919870 is an apocalyptic number.

644919870 is an abundant number, since it is smaller than the sum of its proper divisors (1155595218).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644919870 is a wasteful number, since it uses less digits than its factorization.

644919870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 438745 (or 438738 counting only the distinct ones).

The product of its (nonzero) digits is 435456, while the sum is 48.

The square root of 644919870 is about 25395.2725915671. The cubic root of 644919870 is about 863.9764788050.

The spelling of 644919870 in words is "six hundred forty-four million, nine hundred nineteen thousand, eight hundred seventy".