644278647456 has 240 divisors, whose sum is σ = 2070987367680. Its totient is φ = 195606005760.

The previous prime is 644278647449. The next prime is 644278647511. The reversal of 644278647456 is 654746872446.

644278647456 is a `hidden beast` number, since 6 + 4 + 42 + 78 + 6 + 474 + 56 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 644278647393 and 644278647402.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1130155 + ... + 1601813.

It is an arithmetic number, because the mean of its divisors is an integer number (8629114032).

Almost surely, 2^644278647456 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644278647456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1035493683840).

644278647456 is an abundant number, since it is smaller than the sum of its proper divisors (1426708720224).

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

644278647456 is a wasteful number, since it uses less digits than its factorization.

644278647456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 471729 (or 471712 counting only the distinct ones).

The product of its digits is 216760320, while the sum is 63.

The spelling of 644278647456 in words is "six hundred forty-four billion, two hundred seventy-eight million, six hundred forty-seven thousand, four hundred fifty-six".