644799767040 has 1920 divisors, whose sum is σ = 2800332767232. Its totient is φ = 134886850560.

The previous prime is 644799767011. The next prime is 644799767041. The reversal of 644799767040 is 40767997446.

644799767040 is a `hidden beast` number, since 6 + 4 + 479 + 97 + 6 + 70 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1920).

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

It is not an unprimeable number, because it can be changed into a prime (644799767041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 5077163457 + ... + 5077163583.

Almost surely, 2^644799767040 is an apocalyptic number.

644799767040 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 644799767040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1400166383616).

644799767040 is an abundant number, since it is smaller than the sum of its proper divisors (2155533000192).

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

644799767040 is a wasteful number, since it uses less digits than its factorization.

644799767040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 270 (or 251 counting only the distinct ones).

The product of its (nonzero) digits is 64012032, while the sum is 63.

The spelling of 644799767040 in words is "six hundred forty-four billion, seven hundred ninety-nine million, seven hundred sixty-seven thousand, forty".