644685613 has 8 divisors (see below), whose sum is σ = 757393056. Its totient is φ = 540994800.

The previous prime is 644685589. The next prime is 644685647. The reversal of 644685613 is 316586446.

It is a happy number.

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 644685613 - 2⁵ = 644685581 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644685613.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644685313) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2254003 + ... + 2254288.

It is an arithmetic number, because the mean of its divisors is an integer number (94674132).

Almost surely, 2^644685613 is an apocalyptic number.

It is an amenable number.

644685613 is a deficient number, since it is larger than the sum of its proper divisors (112707443).

644685613 is a wasteful number, since it uses less digits than its factorization.

644685613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4508315.

The product of its digits is 414720, while the sum is 43.

The square root of 644685613 is about 25390.6599559759. The cubic root of 644685613 is about 863.8718575139.

The spelling of 644685613 in words is "six hundred forty-four million, six hundred eighty-five thousand, six hundred thirteen".