644684 has 12 divisors (see below), whose sum is σ = 1156008. Its totient is φ = 314400.

The previous prime is 644671. The next prime is 644687. The reversal of 644684 is 486446.

644684 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 644684.

It is not an unprimeable number, because it can be changed into a prime (644687) by changing a digit.

644684 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1802 + ... + 2129.

It is an arithmetic number, because the mean of its divisors is an integer number (96334).

2⁶⁴⁴⁶⁸⁴ is an apocalyptic number.

It is an amenable number.

644684 is a deficient number, since it is larger than the sum of its proper divisors (511324).

644684 is a wasteful number, since it uses less digits than its factorization.

644684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3976 (or 3974 counting only the distinct ones).

The product of its digits is 18432, while the sum is 32.

The square root of 644684 is about 802.9221631018. The cubic root of 644684 is about 86.3871137046.

The spelling of 644684 in words is "six hundred forty-four thousand, six hundred eighty-four".