644531685 has 32 divisors (see below), whose sum is σ = 1207325952. Its totient is φ = 287454720.

The previous prime is 644531669. The next prime is 644531717. The reversal of 644531685 is 586135446.

It is not a de Polignac number, because 644531685 - 2⁴ = 644531669 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 70554 + ... + 79163.

It is an arithmetic number, because the mean of its divisors is an integer number (37728936).

Almost surely, 2^644531685 is an apocalyptic number.

It is an amenable number.

644531685 is a deficient number, since it is larger than the sum of its proper divisors (562794267).

644531685 is a wasteful number, since it uses less digits than its factorization.

644531685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149773.

The product of its digits is 345600, while the sum is 42.

The square root of 644531685 is about 25387.6285816537. The cubic root of 644531685 is about 863.8030980808.

The spelling of 644531685 in words is "six hundred forty-four million, five hundred thirty-one thousand, six hundred eighty-five".