644045 has 8 divisors (see below), whose sum is σ = 818424. Its totient is φ = 484864.

The previous prime is 644029. The next prime is 644047. The reversal of 644045 is 540446.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 8836 + 635209 = 94^2 + 797^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 644045 - 2⁴ = 644029 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644045.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644045.

It is not an unprimeable number, because it can be changed into a prime (644047) 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, 3704 + ... + 3873.

It is an arithmetic number, because the mean of its divisors is an integer number (102303).

2⁶⁴⁴⁰⁴⁵ is an apocalyptic number.

It is an amenable number.

644045 is a deficient number, since it is larger than the sum of its proper divisors (174379).

644045 is a wasteful number, since it uses less digits than its factorization.

644045 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7599.

The product of its (nonzero) digits is 1920, while the sum is 23.

The square root of 644045 is about 802.5241429390. The cubic root of 644045 is about 86.3585624485.

The spelling of 644045 in words is "six hundred forty-four thousand, forty-five".