644645 has 8 divisors (see below), whose sum is σ = 798720. Its totient is φ = 498960.

The previous prime is 644629. The next prime is 644647. The reversal of 644645 is 546446.

644645 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644645 - 2⁴ = 644629 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644647) 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, 1925 + ... + 2234.

It is an arithmetic number, because the mean of its divisors is an integer number (99840).

2⁶⁴⁴⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

644645 is a deficient number, since it is larger than the sum of its proper divisors (154075).

644645 is a wasteful number, since it uses less digits than its factorization.

644645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4195.

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

The square root of 644645 is about 802.8978764451. The cubic root of 644645 is about 86.3853716804.

The spelling of 644645 in words is "six hundred forty-four thousand, six hundred forty-five".