644565428278 has 16 divisors (see below), whose sum is σ = 967753059840. Its totient is φ = 321981156136.

The previous prime is 644565428263. The next prime is 644565428321. The reversal of 644565428278 is 872824565446.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20612451 + ... + 20643697.

It is an arithmetic number, because the mean of its divisors is an integer number (60484566240).

Almost surely, 2^644565428278 is an apocalyptic number.

644565428278 is a deficient number, since it is larger than the sum of its proper divisors (323187631562).

644565428278 is a wasteful number, since it uses less digits than its factorization.

644565428278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40571.

The product of its digits is 103219200, while the sum is 61.

The spelling of 644565428278 in words is "six hundred forty-four billion, five hundred sixty-five million, four hundred twenty-eight thousand, two hundred seventy-eight".