644261960160 has 1920 divisors, whose sum is σ = 2921143357440. Its totient is φ = 130121220096.

The previous prime is 644261960131. The next prime is 644261960231. The reversal of 644261960160 is 61069162446.

It is a happy number.

644261960160 is a `hidden beast` number, since 6 + 4 + 4 + 26 + 19 + 601 + 6 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

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 319 ways as a sum of consecutive naturals, for example, 3270365182 + ... + 3270365378.

It is an arithmetic number, because the mean of its divisors is an integer number (1521428832).

Almost surely, 2^644261960160 is an apocalyptic number.

644261960160 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 644261960160, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1460571678720).

644261960160 is an abundant number, since it is smaller than the sum of its proper divisors (2276881397280).

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

644261960160 is a wasteful number, since it uses less digits than its factorization.

644261960160 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350 (or 333 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The spelling of 644261960160 in words is "six hundred forty-four billion, two hundred sixty-one million, nine hundred sixty thousand, one hundred sixty".