644996 has 24 divisors (see below), whose sum is σ = 1251936. Its totient is φ = 288320.

The previous prime is 644977. The next prime is 644999. The reversal of 644996 is 699446.

644996 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 not an unprimeable number, because it can be changed into a prime (644999) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4640 + ... + 4776.

It is an arithmetic number, because the mean of its divisors is an integer number (52164).

2⁶⁴⁴⁹⁹⁶ is an apocalyptic number.

It is an amenable number.

644996 is a deficient number, since it is larger than the sum of its proper divisors (606940).

644996 is a wasteful number, since it uses less digits than its factorization.

644996 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259 (or 257 counting only the distinct ones).

The product of its digits is 46656, while the sum is 38.

The square root of 644996 is about 803.1164299154. The cubic root of 644996 is about 86.4010473696.

The spelling of 644996 in words is "six hundred forty-four thousand, nine hundred ninety-six".