644810646081 has 32 divisors (see below), whose sum is σ = 983621816320. Its totient is φ = 368068530816.

The previous prime is 644810646049. The next prime is 644810646133. The reversal of 644810646081 is 180646018446.

It is not a de Polignac number, because 644810646081 - 2⁵ = 644810646049 is a prime.

It is a super-2 number, since 2×644810646081² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644810646081.

It is not an unprimeable number, because it can be changed into a prime (644810646041) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 100325190 + ... + 100331616.

It is an arithmetic number, because the mean of its divisors is an integer number (30738181760).

Almost surely, 2^644810646081 is an apocalyptic number.

It is an amenable number.

644810646081 is a deficient number, since it is larger than the sum of its proper divisors (338811170239).

644810646081 is a wasteful number, since it uses less digits than its factorization.

644810646081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10813.

The product of its (nonzero) digits is 884736, while the sum is 48.

The spelling of 644810646081 in words is "six hundred forty-four billion, eight hundred ten million, six hundred forty-six thousand, eighty-one".