644924 has 24 divisors (see below), whose sum is σ = 1333248. Its totient is φ = 267120.

The previous prime is 644923. The next prime is 644933. The reversal of 644924 is 429446.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644924.

It is not an unprimeable number, because it can be changed into a prime (644923) 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, 497 + ... + 1239.

It is an arithmetic number, because the mean of its divisors is an integer number (55552).

2⁶⁴⁴⁹²⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644924, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (666624).

644924 is an abundant number, since it is smaller than the sum of its proper divisors (688324).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644924 is a wasteful number, since it uses less digits than its factorization.

644924 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 785 (or 783 counting only the distinct ones).

The product of its digits is 6912, while the sum is 29.

The square root of 644924 is about 803.0716032833. The cubic root of 644924 is about 86.3978323073.

The spelling of 644924 in words is "six hundred forty-four thousand, nine hundred twenty-four".