644879 has 4 divisors (see below), whose sum is σ = 678840. Its totient is φ = 610920.

The previous prime is 644869. The next prime is 644881. The reversal of 644879 is 978446.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644879 - 2⁴ = 644863 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 (644869) 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, 16952 + ... + 16989.

It is an arithmetic number, because the mean of its divisors is an integer number (169710).

2⁶⁴⁴⁸⁷⁹ is an apocalyptic number.

644879 is a deficient number, since it is larger than the sum of its proper divisors (33961).

644879 is a wasteful number, since it uses less digits than its factorization.

644879 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33960.

The product of its digits is 48384, while the sum is 38.

The square root of 644879 is about 803.0435853676. The cubic root of 644879 is about 86.3958227719.

The spelling of 644879 in words is "six hundred forty-four thousand, eight hundred seventy-nine".