644731689 has 8 divisors (see below), whose sum is σ = 982448320. Its totient is φ = 368418096.

The previous prime is 644731673. The next prime is 644731721. The reversal of 644731689 is 986137446.

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

It is not a de Polignac number, because 644731689 - 2⁴ = 644731673 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644731669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15350734 + ... + 15350775.

It is an arithmetic number, because the mean of its divisors is an integer number (122806040).

Almost surely, 2^644731689 is an apocalyptic number.

It is an amenable number.

644731689 is a deficient number, since it is larger than the sum of its proper divisors (337716631).

644731689 is a wasteful number, since it uses less digits than its factorization.

644731689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30701519.

The product of its digits is 870912, while the sum is 48.

The square root of 644731689 is about 25391.5672812845. The cubic root of 644731689 is about 863.8924374735.

The spelling of 644731689 in words is "six hundred forty-four million, seven hundred thirty-one thousand, six hundred eighty-nine".