644640046446 has 64 divisors (see below), whose sum is σ = 1445999639040. Its totient is φ = 189868613760.

The previous prime is 644640046423. The next prime is 644640046459.

644640046446 is nontrivially palindromic in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 644640046395 and 644640046404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2224920 + ... + 2497908.

It is an arithmetic number, because the mean of its divisors is an integer number (22593744360).

Almost surely, 2^644640046446 is an apocalyptic number.

644640046446 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 644640046446, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (722999819520).

644640046446 is an abundant number, since it is smaller than the sum of its proper divisors (801359592594).

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

644640046446 is a wasteful number, since it uses less digits than its factorization.

644640046446 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274009.

The product of its (nonzero) digits is 5308416, while the sum is 48.

The spelling of 644640046446 in words is "six hundred forty-four billion, six hundred forty million, forty-six thousand, four hundred forty-six".