644785 has 8 divisors (see below), whose sum is σ = 792000. Its totient is φ = 503664.

The previous prime is 644783. The next prime is 644789. The reversal of 644785 is 587446.

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

It is a cyclic number.

It is not a de Polignac number, because 644785 - 2¹ = 644783 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644785.

It is not an unprimeable number, because it can be changed into a prime (644783) 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, 1285 + ... + 1714.

It is an arithmetic number, because the mean of its divisors is an integer number (99000).

2⁶⁴⁴⁷⁸⁵ is an apocalyptic number.

It is an amenable number.

644785 is a deficient number, since it is larger than the sum of its proper divisors (147215).

644785 is a wasteful number, since it uses less digits than its factorization.

644785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3047.

The product of its digits is 26880, while the sum is 34.

The square root of 644785 is about 802.9850559008. The cubic root of 644785 is about 86.3916247740.

The spelling of 644785 in words is "six hundred forty-four thousand, seven hundred eighty-five".