644471372870640 has 1920 divisors, whose sum is σ = 2793664658304000. Its totient is φ = 135684647755776.

The previous prime is 644471372870543. The next prime is 644471372870669. The reversal of 644471372870640 is 46078273174446.

644471372870640 is a `hidden beast` number, since 6 + 4 + 4 + 471 + 37 + 2 + 8 + 70 + 64 + 0 = 666.

It is a hoax number, since the sum of its digits (63) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (63).

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, 152754530451 + ... + 152754534669.

It is an arithmetic number, because the mean of its divisors is an integer number (1455033676200).

Almost surely, 2^{644471372870640} is an apocalyptic number.

644471372870640 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 644471372870640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1396832329152000).

644471372870640 is an abundant number, since it is smaller than the sum of its proper divisors (2149193285433360).

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

644471372870640 is a wasteful number, since it uses less digits than its factorization.

644471372870640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6364 (or 6345 counting only the distinct ones).

The product of its (nonzero) digits is 151732224, while the sum is 63.

The spelling of 644471372870640 in words is "six hundred forty-four trillion, four hundred seventy-one billion, three hundred seventy-two million, eight hundred seventy thousand, six hundred forty".