644547870720 has 760 divisors, whose sum is σ = 2493903235824. Its totient is φ = 158318198784.

The previous prime is 644547870697. The next prime is 644547870721. The reversal of 644547870720 is 27078745446.

644547870720 is a `hidden beast` number, since 6 + 4 + 4 + 547 + 8 + 70 + 7 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (644547870721) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1380187927 + ... + 1380188393.

Almost surely, 2^644547870720 is an apocalyptic number.

644547870720 is a gapful number since it is divisible by the number (60) 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 644547870720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1246951617912).

644547870720 is an abundant number, since it is smaller than the sum of its proper divisors (1849355365104).

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

644547870720 is an frugal number, since it uses more digits than its factorization.

644547870720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 533 (or 490 counting only the distinct ones).

The product of its (nonzero) digits is 10536960, while the sum is 54.

The spelling of 644547870720 in words is "six hundred forty-four billion, five hundred forty-seven million, eight hundred seventy thousand, seven hundred twenty".