644816 has 20 divisors (see below), whose sum is σ = 1261824. Its totient is φ = 319200.

The previous prime is 644801. The next prime is 644837. The reversal of 644816 is 618446.

644816 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644816.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2951 + ... + 3161.

2⁶⁴⁴⁸¹⁶ is an apocalyptic number.

It is an amenable number.

644816 is a deficient number, since it is larger than the sum of its proper divisors (617008).

644816 is a wasteful number, since it uses less digits than its factorization.

644816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410 (or 404 counting only the distinct ones).

The product of its digits is 4608, while the sum is 29.

The square root of 644816 is about 803.0043586432. The cubic root of 644816 is about 86.3930092652.

The spelling of 644816 in words is "six hundred forty-four thousand, eight hundred sixteen".