644045540406 has 16 divisors (see below), whose sum is σ = 1297357924800. Its totient is φ = 213137372808.

The previous prime is 644045540389. The next prime is 644045540407. The reversal of 644045540406 is 604045540446.

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 7 ways as a sum of consecutive naturals, for example, 386117596 + ... + 386119263.

It is an arithmetic number, because the mean of its divisors is an integer number (81084870300).

Almost surely, 2^644045540406 is an apocalyptic number.

644045540406 is an abundant number, since it is smaller than the sum of its proper divisors (653312384394).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644045540406 is a wasteful number, since it uses less digits than its factorization.

644045540406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 772237003.

The product of its (nonzero) digits is 921600, while the sum is 42.

The spelling of 644045540406 in words is "six hundred forty-four billion, forty-five million, five hundred forty thousand, four hundred six".