644424 has 32 divisors (see below), whose sum is σ = 1758240. Its totient is φ = 195200.

The previous prime is 644411. The next prime is 644431. The reversal of 644424 is 424446.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 644394 and 644403.

It is a congruent number.

It is an unprimeable number.

644424 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 957 + ... + 1484.

It is an arithmetic number, because the mean of its divisors is an integer number (54945).

2⁶⁴⁴⁴²⁴ is an apocalyptic number.

It is an amenable number.

644424 is an abundant number, since it is smaller than the sum of its proper divisors (1113816).

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

644424 is a wasteful number, since it uses less digits than its factorization.

644424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2461 (or 2457 counting only the distinct ones).

The product of its digits is 3072, while the sum is 24.

The square root of 644424 is about 802.7602381782. The cubic root of 644424 is about 86.3754988826.

It can be divided in two parts, 64442 and 4, that added together give a palindrome (64446).

The spelling of 644424 in words is "six hundred forty-four thousand, four hundred twenty-four".