644505 has 8 divisors (see below), whose sum is σ = 1031232. Its totient is φ = 343728.

The previous prime is 644491. The next prime is 644507. The reversal of 644505 is 505446.

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

It is not a de Polignac number, because 644505 - 2⁴ = 644489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644507) 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, 21469 + ... + 21498.

It is an arithmetic number, because the mean of its divisors is an integer number (128904).

2⁶⁴⁴⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

644505 is a deficient number, since it is larger than the sum of its proper divisors (386727).

644505 is a wasteful number, since it uses less digits than its factorization.

644505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42975.

The product of its (nonzero) digits is 2400, while the sum is 24.

The square root of 644505 is about 802.8106875223. The cubic root of 644505 is about 86.3791176813.

The spelling of 644505 in words is "six hundred forty-four thousand, five hundred five".