644816055778 has 16 divisors (see below), whose sum is σ = 1010221513920. Its totient is φ = 308101779216.

The previous prime is 644816055773. The next prime is 644816055781. The reversal of 644816055778 is 877550618446.

It is not an unprimeable number, because it can be changed into a prime (644816055773) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6507300 + ... + 6605647.

It is an arithmetic number, because the mean of its divisors is an integer number (63138844620).

Almost surely, 2^644816055778 is an apocalyptic number.

644816055778 is a deficient number, since it is larger than the sum of its proper divisors (365405458142).

644816055778 is a wasteful number, since it uses less digits than its factorization.

644816055778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13114041.

The product of its (nonzero) digits is 45158400, while the sum is 61.

The spelling of 644816055778 in words is "six hundred forty-four billion, eight hundred sixteen million, fifty-five thousand, seven hundred seventy-eight".