644816055787 has 4 divisors (see below), whose sum is σ = 646642730520. Its totient is φ = 642989381056.

The previous prime is 644816055781. The next prime is 644816055797. The reversal of 644816055787 is 787550618446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644816055787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644816055781) 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 3 ways as a sum of consecutive naturals, for example, 913336837 + ... + 913337542.

It is an arithmetic number, because the mean of its divisors is an integer number (161660682630).

Almost surely, 2^644816055787 is an apocalyptic number.

644816055787 is a deficient number, since it is larger than the sum of its proper divisors (1826674733).

644816055787 is a wasteful number, since it uses less digits than its factorization.

644816055787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1826674732.

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

The spelling of 644816055787 in words is "six hundred forty-four billion, eight hundred sixteen million, fifty-five thousand, seven hundred eighty-seven".