644455 has 8 divisors (see below), whose sum is σ = 883872. Its totient is φ = 441888.

The previous prime is 644447. The next prime is 644489. The reversal of 644455 is 554446.

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 644455 - 2³ = 644447 is a prime.

It is a Duffinian number.

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, 9172 + ... + 9241.

It is an arithmetic number, because the mean of its divisors is an integer number (110484).

2⁶⁴⁴⁴⁵⁵ is an apocalyptic number.

644455 is a deficient number, since it is larger than the sum of its proper divisors (239417).

644455 is a wasteful number, since it uses less digits than its factorization.

644455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18425.

The product of its digits is 9600, while the sum is 28.

The square root of 644455 is about 802.7795463264. The cubic root of 644455 is about 86.3768838908.

Subtracting from 644455 its reverse (554446), we obtain a palindrome (90009).

The spelling of 644455 in words is "six hundred forty-four thousand, four hundred fifty-five".