644279 has 4 divisors (see below), whose sum is σ = 650760. Its totient is φ = 637800.

The previous prime is 644261. The next prime is 644291. The reversal of 644279 is 972446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 972446 = 2 ⋅486223.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644279 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 (644239) 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, 3089 + ... + 3290.

It is an arithmetic number, because the mean of its divisors is an integer number (162690).

2⁶⁴⁴²⁷⁹ is an apocalyptic number.

644279 is a deficient number, since it is larger than the sum of its proper divisors (6481).

644279 is a wasteful number, since it uses less digits than its factorization.

644279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6480.

The product of its digits is 12096, while the sum is 32.

The square root of 644279 is about 802.6699197055. The cubic root of 644279 is about 86.3690200287.

The spelling of 644279 in words is "six hundred forty-four thousand, two hundred seventy-nine".