644169 has 4 divisors (see below), whose sum is σ = 858896. Its totient is φ = 429444.

The previous prime is 644159. The next prime is 644173. The reversal of 644169 is 961446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 644169 - 2⁴ = 644153 is a prime.

It is a super-2 number, since 2×644169² = 829907401122, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644129) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107359 + ... + 107364.

It is an arithmetic number, because the mean of its divisors is an integer number (214724).

2⁶⁴⁴¹⁶⁹ is an apocalyptic number.

It is an amenable number.

644169 is a deficient number, since it is larger than the sum of its proper divisors (214727).

644169 is a wasteful number, since it uses less digits than its factorization.

644169 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214726.

The product of its digits is 5184, while the sum is 30.

The square root of 644169 is about 802.6013954635. The cubic root of 644169 is about 86.3641043876.

The spelling of 644169 in words is "six hundred forty-four thousand, one hundred sixty-nine".