644255 has 8 divisors (see below), whose sum is σ = 777600. Its totient is φ = 512416.

The previous prime is 644239. The next prime is 644257. The reversal of 644255 is 552446.

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 644255 - 2⁴ = 644239 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644257) 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, 1106 + ... + 1584.

It is an arithmetic number, because the mean of its divisors is an integer number (97200).

2⁶⁴⁴²⁵⁵ is an apocalyptic number.

644255 is a deficient number, since it is larger than the sum of its proper divisors (133345).

644255 is a wasteful number, since it uses less digits than its factorization.

644255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 753.

The product of its digits is 4800, while the sum is 26.

The square root of 644255 is about 802.6549694607. The cubic root of 644255 is about 86.3679475729.

Subtracting from 644255 its reverse (552446), we obtain a square (91809 = 303²).

The spelling of 644255 in words is "six hundred forty-four thousand, two hundred fifty-five".