644045540405 has 16 divisors (see below), whose sum is σ = 783278138880. Its totient is φ = 508298114688.

The previous prime is 644045540389. The next prime is 644045540407. The reversal of 644045540405 is 504045540446.

It is a cyclic number.

It is not a de Polignac number, because 644045540405 - 2⁴ = 644045540389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644045540407) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 183512 + ... + 1149681.

It is an arithmetic number, because the mean of its divisors is an integer number (48954883680).

Almost surely, 2^644045540405 is an apocalyptic number.

It is an amenable number.

644045540405 is a deficient number, since it is larger than the sum of its proper divisors (139232598475).

644045540405 is a wasteful number, since it uses less digits than its factorization.

644045540405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1334500.

The product of its (nonzero) digits is 768000, while the sum is 41.

Adding to 644045540405 its sum of digits (41), we get a palindrome (644045540446).

The spelling of 644045540405 in words is "six hundred forty-four billion, forty-five million, five hundred forty thousand, four hundred five".