644660004 has 48 divisors (see below), whose sum is σ = 1571512320. Its totient is φ = 205439520.

The previous prime is 644659979. The next prime is 644660011. The reversal of 644660004 is 400066446.

644660004 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, 20437 + ... + 41315.

It is an arithmetic number, because the mean of its divisors is an integer number (32739840).

Almost surely, 2^644660004 is an apocalyptic number.

It is an amenable number.

644660004 is an abundant number, since it is smaller than the sum of its proper divisors (926852316).

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

644660004 is a wasteful number, since it uses less digits than its factorization.

644660004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21000 (or 20998 counting only the distinct ones).

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

The square root of 644660004 is about 25390.1556513543. The cubic root of 644660004 is about 863.8604187667.

The spelling of 644660004 in words is "six hundred forty-four million, six hundred sixty thousand, four".