644636 has 6 divisors (see below), whose sum is σ = 1128120. Its totient is φ = 322316.

The previous prime is 644629. The next prime is 644647. The reversal of 644636 is 636446.

644636 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 644599 and 644608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80576 + ... + 80583.

It is an arithmetic number, because the mean of its divisors is an integer number (188020).

2⁶⁴⁴⁶³⁶ is an apocalyptic number.

It is an amenable number.

644636 is a deficient number, since it is larger than the sum of its proper divisors (483484).

644636 is a wasteful number, since it uses less digits than its factorization.

644636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161163 (or 161161 counting only the distinct ones).

The product of its digits is 10368, while the sum is 29.

The square root of 644636 is about 802.8922717277. The cubic root of 644636 is about 86.3849696648.

The spelling of 644636 in words is "six hundred forty-four thousand, six hundred thirty-six".