644040660 has 48 divisors (see below), whose sum is σ = 1805126400. Its totient is φ = 171571584.

The previous prime is 644040629. The next prime is 644040673. The reversal of 644040660 is 66040446.

644040660 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

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, 61701 + ... + 71379.

It is an arithmetic number, because the mean of its divisors is an integer number (37606800).

Almost surely, 2^644040660 is an apocalyptic number.

644040660 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644040660 is an abundant number, since it is smaller than the sum of its proper divisors (1161085740).

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

644040660 is a wasteful number, since it uses less digits than its factorization.

644040660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10800 (or 10798 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 30.

The square root of 644040660 is about 25377.9561824825. The cubic root of 644040660 is about 863.5836846774.

The spelling of 644040660 in words is "six hundred forty-four million, forty thousand, six hundred sixty".