644275 has 6 divisors (see below), whose sum is σ = 798932. Its totient is φ = 515400.

The previous prime is 644261. The next prime is 644291. The reversal of 644275 is 572446.

It is not a de Polignac number, because 644275 - 2¹⁷ = 513203 is a prime.

It is a Duffinian number.

644275 is a lucky number.

It is an unprimeable number.

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 5 ways as a sum of consecutive naturals, for example, 12861 + ... + 12910.

2⁶⁴⁴²⁷⁵ is an apocalyptic number.

644275 is a deficient number, since it is larger than the sum of its proper divisors (154657).

644275 is a wasteful number, since it uses less digits than its factorization.

644275 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25781 (or 25776 counting only the distinct ones).

The product of its digits is 6720, while the sum is 28.

The square root of 644275 is about 802.6674280174. The cubic root of 644275 is about 86.3688412879.

It can be divided in two parts, 644 and 275, that added together give a palindrome (919).

The spelling of 644275 in words is "six hundred forty-four thousand, two hundred seventy-five".