644493986 has 16 divisors (see below), whose sum is σ = 990157824. Its totient is φ = 314481024.

The previous prime is 644493977. The next prime is 644494007. The reversal of 644493986 is 689394446.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 23471 + ... + 42893.

It is an arithmetic number, because the mean of its divisors is an integer number (61884864).

Almost surely, 2^644493986 is an apocalyptic number.

644493986 is a deficient number, since it is larger than the sum of its proper divisors (345663838).

644493986 is a wasteful number, since it uses less digits than its factorization.

644493986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19825.

The product of its digits is 4478976, while the sum is 53.

The square root of 644493986 is about 25386.8861028681. The cubic root of 644493986 is about 863.7862563187.

The spelling of 644493986 in words is "six hundred forty-four million, four hundred ninety-three thousand, nine hundred eighty-six".