644927855 has 16 divisors (see below), whose sum is σ = 909213984. Its totient is φ = 432958080.

The previous prime is 644927831. The next prime is 644927869. The reversal of 644927855 is 558729446.

It is a de Polignac number, because none of the positive numbers 2^k-644927855 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 450284 + ... + 451713.

It is an arithmetic number, because the mean of its divisors is an integer number (56825874).

Almost surely, 2^644927855 is an apocalyptic number.

644927855 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

644927855 is a deficient number, since it is larger than the sum of its proper divisors (264286129).

644927855 is a wasteful number, since it uses less digits than its factorization.

644927855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 902026.

The product of its digits is 2419200, while the sum is 50.

The square root of 644927855 is about 25395.4298053803. The cubic root of 644927855 is about 863.9800445315.

The spelling of 644927855 in words is "six hundred forty-four million, nine hundred twenty-seven thousand, eight hundred fifty-five".