644770 has 32 divisors (see below), whose sum is σ = 1357056. Its totient is φ = 216000.

The previous prime is 644767. The next prime is 644783. The reversal of 644770 is 77446.

644770 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4195 + ... + 4345.

It is an arithmetic number, because the mean of its divisors is an integer number (42408).

2⁶⁴⁴⁷⁷⁰ is an apocalyptic number.

644770 is an abundant number, since it is smaller than the sum of its proper divisors (712286).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644770 is a wasteful number, since it uses less digits than its factorization.

644770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226.

The product of its (nonzero) digits is 4704, while the sum is 28.

The square root of 644770 is about 802.9757156976. The cubic root of 644770 is about 86.3909548430.

The spelling of 644770 in words is "six hundred forty-four thousand, seven hundred seventy".