644641615 has 16 divisors (see below), whose sum is σ = 820501920. Its totient is φ = 484531200.

The previous prime is 644641607. The next prime is 644641619. The reversal of 644641615 is 516146446.

It is not a de Polignac number, because 644641615 - 2³ = 644641607 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644641619) 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 15 ways as a sum of consecutive naturals, for example, 44776 + ... + 57394.

It is an arithmetic number, because the mean of its divisors is an integer number (51281370).

Almost surely, 2^644641615 is an apocalyptic number.

644641615 is a deficient number, since it is larger than the sum of its proper divisors (175860305).

644641615 is a wasteful number, since it uses less digits than its factorization.

644641615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13242.

The product of its digits is 69120, while the sum is 37.

The square root of 644641615 is about 25389.7935202317. The cubic root of 644641615 is about 863.8522047830.

The spelling of 644641615 in words is "six hundred forty-four million, six hundred forty-one thousand, six hundred fifteen".