644224 has 32 divisors (see below), whose sum is σ = 1468800. Its totient is φ = 275712.

The previous prime is 644201. The next prime is 644227. The reversal of 644224 is 422446.

It is a tau number, because it is divible by the number of its divisors (32).

It is a junction number, because it is equal to n+sod(n) for n = 644195 and 644204.

It is not an unprimeable number, because it can be changed into a prime (644227) by changing a digit.

644224 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 537 + ... + 1255.

It is an arithmetic number, because the mean of its divisors is an integer number (45900).

2⁶⁴⁴²²⁴ is an apocalyptic number.

644224 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (734400).

644224 is an abundant number, since it is smaller than the sum of its proper divisors (824576).

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

644224 is an equidigital number, since it uses as much as digits as its factorization.

644224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 740 (or 728 counting only the distinct ones).

The product of its digits is 1536, while the sum is 22.

The square root of 644224 is about 802.6356583158. The cubic root of 644224 is about 86.3665622781.

It can be divided in two parts, 644 and 224, that added together give a palindrome (868).

The spelling of 644224 in words is "six hundred forty-four thousand, two hundred twenty-four".