644687617 has 12 divisors (see below), whose sum is σ = 782678080. Its totient is φ = 520082496.

The previous prime is 644687599. The next prime is 644687621. The reversal of 644687617 is 716786446.

It is not a de Polignac number, because 644687617 - 2²³ = 636299009 is a prime.

It is a hoax number, since the sum of its digits (49) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644687627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 157317 + ... + 161362.

Almost surely, 2^644687617 is an apocalyptic number.

It is an amenable number.

644687617 is a deficient number, since it is larger than the sum of its proper divisors (137990463).

644687617 is a wasteful number, since it uses less digits than its factorization.

644687617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 318720 (or 318703 counting only the distinct ones).

The product of its digits is 1354752, while the sum is 49.

The square root of 644687617 is about 25390.6994192756. The cubic root of 644687617 is about 863.8727526259.

The spelling of 644687617 in words is "six hundred forty-four million, six hundred eighty-seven thousand, six hundred seventeen".