644475 has 24 divisors (see below), whose sum is σ = 1149232. Its totient is φ = 316800.

The previous prime is 644447. The next prime is 644489. The reversal of 644475 is 574446.

It is not a de Polignac number, because 644475 - 2⁵ = 644443 is a prime.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 645 + ... + 1305.

2⁶⁴⁴⁴⁷⁵ is an apocalyptic number.

644475 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

644475 is a deficient number, since it is larger than the sum of its proper divisors (504757).

644475 is a wasteful number, since it uses less digits than its factorization.

644475 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 687 (or 682 counting only the distinct ones).

The product of its digits is 13440, while the sum is 30.

The square root of 644475 is about 802.7920029497. The cubic root of 644475 is about 86.3777774209.

The spelling of 644475 in words is "six hundred forty-four thousand, four hundred seventy-five".