644403 has 8 divisors (see below), whose sum is σ = 870400. Its totient is φ = 424008.

The previous prime is 644401. The next prime is 644411. The reversal of 644403 is 304446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644403 - 2¹ = 644401 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644403.

It is not an unprimeable number, because it can be changed into a prime (644401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1123 + ... + 1596.

It is an arithmetic number, because the mean of its divisors is an integer number (108800).

2⁶⁴⁴⁴⁰³ is an apocalyptic number.

644403 is a deficient number, since it is larger than the sum of its proper divisors (225997).

644403 is a wasteful number, since it uses less digits than its factorization.

644403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2801.

The product of its (nonzero) digits is 1152, while the sum is 21.

The square root of 644403 is about 802.7471582011. The cubic root of 644403 is about 86.3745606260.

Adding to 644403 its reverse (304446), we get a palindrome (948849).

The spelling of 644403 in words is "six hundred forty-four thousand, four hundred three".