644843294244864 has 5760 divisors, whose sum is σ = 2651293666344960. Its totient is φ = 151727269478400.

The previous prime is 644843294244839. The next prime is 644843294244883. The reversal of 644843294244864 is 468442492348446.

644843294244864 is a `hidden beast` number, since 6 + 4 + 4 + 8 + 4 + 32 + 94 + 2 + 448 + 64 = 666.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 644843294244792 and 644843294244801.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 383 ways as a sum of consecutive naturals, for example, 20801396588529 + ... + 20801396588559.

It is an arithmetic number, because the mean of its divisors is an integer number (460294039296).

Almost surely, 2^{644843294244864} is an apocalyptic number.

644843294244864 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644843294244864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1325646833172480).

644843294244864 is an abundant number, since it is smaller than the sum of its proper divisors (2006450372100096).

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

644843294244864 is a wasteful number, since it uses less digits than its factorization.

644843294244864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 190 (or 129 counting only the distinct ones).

The product of its digits is 4076863488, while the sum is 72.

The spelling of 644843294244864 in words is "six hundred forty-four trillion, eight hundred forty-three billion, two hundred ninety-four million, two hundred forty-four thousand, eight hundred sixty-four".