644023138455 has 12 divisors (see below), whose sum is σ = 1116306773400. Its totient is φ = 343479007152.

The previous prime is 644023138403. The next prime is 644023138457. The reversal of 644023138455 is 554831320446.

644023138455 is a `hidden beast` number, since 6 + 4 + 40 + 23 + 138 + 455 = 666.

It is not a de Polignac number, because 644023138455 - 2⁹ = 644023137943 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 14311625299 = 644023138455 / (6 + 4 + 4 + 0 + 2 + 3 + 1 + 3 + 8 + 4 + 5 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 644023138455.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644023138457) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7155812605 + ... + 7155812694.

It is an arithmetic number, because the mean of its divisors is an integer number (93025564450).

Almost surely, 2^644023138455 is an apocalyptic number.

644023138455 is a deficient number, since it is larger than the sum of its proper divisors (472283634945).

644023138455 is a wasteful number, since it uses less digits than its factorization.

644023138455 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14311625310 (or 14311625307 counting only the distinct ones).

The product of its (nonzero) digits is 1382400, while the sum is 45.

The spelling of 644023138455 in words is "six hundred forty-four billion, twenty-three million, one hundred thirty-eight thousand, four hundred fifty-five".