644365 has 4 divisors (see below), whose sum is σ = 773244.
Its totient is φ = 515488.
The previous prime is 644363. The next prime is 644377. The reversal of 644365 is 563446.
644365 is nontrivially palindromic in base 9.
644365 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a semiprime because it is the product of two primes.
It can be written as a sum of positive squares in 2 ways, for example, as 362404 + 281961 = 602^2 + 531^2
It is a cyclic number.
It is not a de Polignac number, because 644365 - 21 = 644363 is a prime.
It is a Duffinian number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (644363) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64432 + ... + 64441.
It is an arithmetic number, because the mean of its divisors is an integer number (193311).
2644365 is an apocalyptic number.
It is an amenable number.
644365 is a deficient number, since it is larger than the sum of its proper divisors (128879).
644365 is a wasteful number, since it uses less digits than its factorization.
644365 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 128878.
The product of its digits is 8640, while the sum is 28.
The square root of 644365 is about 802.7234891294.
The cubic root of 644365 is about 86.3728627766.
The spelling of 644365 in words is "six hundred forty-four thousand, three hundred sixty-five".