644981513 has 32 divisors (see below), whose sum is σ = 760586112. Its totient is φ = 540467200.

The previous prime is 644981509. The next prime is 644981527. The reversal of 644981513 is 315189446.

It is a cyclic number.

It is not a de Polignac number, because 644981513 - 2² = 644981509 is a prime.

It is a super-2 number, since 2×644981513² = 832002304223538338, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644981503) 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 31 ways as a sum of consecutive naturals, for example, 2768045 + ... + 2768277.

It is an arithmetic number, because the mean of its divisors is an integer number (23768316).

Almost surely, 2^644981513 is an apocalyptic number.

It is an amenable number.

644981513 is a deficient number, since it is larger than the sum of its proper divisors (115604599).

644981513 is a wasteful number, since it uses less digits than its factorization.

644981513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 505.

The product of its digits is 103680, while the sum is 41.

The square root of 644981513 is about 25396.4862333355. The cubic root of 644981513 is about 864.0040049147.

The spelling of 644981513 in words is "six hundred forty-four million, nine hundred eighty-one thousand, five hundred thirteen".