644691305 has 8 divisors (see below), whose sum is σ = 774274632. Its totient is φ = 515323008.

The previous prime is 644691301. The next prime is 644691319. The reversal of 644691305 is 503196446.

It can be written as a sum of positive squares in 4 ways, for example, as 6270016 + 638421289 = 2504^2 + 25267^2 .

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 644691305 - 2² = 644691301 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644691301) 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, 47084 + ... + 59213.

It is an arithmetic number, because the mean of its divisors is an integer number (96784329).

Almost surely, 2^644691305 is an apocalyptic number.

It is an amenable number.

644691305 is a deficient number, since it is larger than the sum of its proper divisors (129583327).

644691305 is a wasteful number, since it uses less digits than its factorization.

644691305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107515.

The product of its (nonzero) digits is 77760, while the sum is 38.

The square root of 644691305 is about 25390.7720441896. The cubic root of 644691305 is about 863.8743999129.

The spelling of 644691305 in words is "six hundred forty-four million, six hundred ninety-one thousand, three hundred five".