644456 has 8 divisors (see below), whose sum is σ = 1208370. Its totient is φ = 322224.

The previous prime is 644447. The next prime is 644489. The reversal of 644456 is 654446.

644456 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 532900 + 111556 = 730^2 + 334^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40271 + ... + 40286.

2⁶⁴⁴⁴⁵⁶ is an apocalyptic number.

It is an amenable number.

644456 is a deficient number, since it is larger than the sum of its proper divisors (563914).

644456 is a wasteful number, since it uses less digits than its factorization.

644456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80563 (or 80559 counting only the distinct ones).

The product of its digits is 11520, while the sum is 29.

The square root of 644456 is about 802.7801691621. The cubic root of 644456 is about 86.3769285677.

The spelling of 644456 in words is "six hundred forty-four thousand, four hundred fifty-six".