644866505 has 8 divisors (see below), whose sum is σ = 775257792. Its totient is φ = 514947888.

The previous prime is 644866501. The next prime is 644866507. The reversal of 644866505 is 505668446.

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 644866505 - 2² = 644866501 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644866501) 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, 115157 + ... + 120626.

It is an arithmetic number, because the mean of its divisors is an integer number (96907224).

Almost surely, 2^644866505 is an apocalyptic number.

It is an amenable number.

644866505 is a deficient number, since it is larger than the sum of its proper divisors (130391287).

644866505 is a wasteful number, since it uses less digits than its factorization.

644866505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 236335.

The product of its (nonzero) digits is 691200, while the sum is 44.

The square root of 644866505 is about 25394.2218821526. The cubic root of 644866505 is about 863.9526477428.

The spelling of 644866505 in words is "six hundred forty-four million, eight hundred sixty-six thousand, five hundred five".