644870 has 16 divisors (see below), whose sum is σ = 1181520. Its totient is φ = 253344.

The previous prime is 644869. The next prime is 644881. The reversal of 644870 is 78446.

644870 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 unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44 + ... + 1136.

It is an arithmetic number, because the mean of its divisors is an integer number (73845).

2⁶⁴⁴⁸⁷⁰ is an apocalyptic number.

644870 is a deficient number, since it is larger than the sum of its proper divisors (536650).

644870 is a wasteful number, since it uses less digits than its factorization.

644870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1159.

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 644870 is about 803.0379816671. The cubic root of 644870 is about 86.3954208536.

The spelling of 644870 in words is "six hundred forty-four thousand, eight hundred seventy".