644539620 has 48 divisors (see below), whose sum is σ = 1814823360. Its totient is φ = 170914176.

The previous prime is 644539607. The next prime is 644539663. The reversal of 644539620 is 26935446.

644539620 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19267 + ... + 40746.

It is an arithmetic number, because the mean of its divisors is an integer number (37808820).

Almost surely, 2^644539620 is an apocalyptic number.

644539620 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644539620 is an abundant number, since it is smaller than the sum of its proper divisors (1170283740).

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

644539620 is a wasteful number, since it uses less digits than its factorization.

644539620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60204 (or 60202 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 39.

The square root of 644539620 is about 25387.7848580769. The cubic root of 644539620 is about 863.8066429024.

The spelling of 644539620 in words is "six hundred forty-four million, five hundred thirty-nine thousand, six hundred twenty".