644775339133440 has 960 divisors, whose sum is σ = 2339928975960576. Its totient is φ = 163907143335936.

The previous prime is 644775339133427. The next prime is 644775339133559. The reversal of 644775339133440 is 44331933577446.

644775339133440 is a `hidden beast` number, since 6 + 4 + 4 + 7 + 7 + 53 + 3 + 9 + 133 + 440 = 666.

It is a tau number, because it is divible by the number of its divisors (960).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 33569800317 + ... + 33569819523.

Almost surely, 2^{644775339133440} is an apocalyptic number.

644775339133440 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 644775339133440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1169964487980288).

644775339133440 is an abundant number, since it is smaller than the sum of its proper divisors (1695153636827136).

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

644775339133440 is a wasteful number, since it uses less digits than its factorization.

644775339133440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20069 (or 20050 counting only the distinct ones).

The product of its (nonzero) digits is 274337280, while the sum is 63.

The spelling of 644775339133440 in words is "six hundred forty-four trillion, seven hundred seventy-five billion, three hundred thirty-nine million, one hundred thirty-three thousand, four hundred forty".