644669706240 has 624 divisors, whose sum is σ = 2595990798336. Its totient is φ = 144919756800.

The previous prime is 644669706221. The next prime is 644669706257. The reversal of 644669706240 is 42607966446.

It is a happy number.

644669706240 is a `hidden beast` number, since 6 + 4 + 4 + 6 + 6 + 9 + 7 + 0 + 624 + 0 = 666.

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 47 ways as a sum of consecutive naturals, for example, 78700545 + ... + 78708735.

It is an arithmetic number, because the mean of its divisors is an integer number (4160241664).

Almost surely, 2^644669706240 is an apocalyptic number.

644669706240 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 644669706240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1297995399168).

644669706240 is an abundant number, since it is smaller than the sum of its proper divisors (1951321092096).

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

644669706240 is a wasteful number, since it uses less digits than its factorization.

644669706240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8294 (or 8269 counting only the distinct ones).

The product of its (nonzero) digits is 10450944, while the sum is 54.

The spelling of 644669706240 in words is "six hundred forty-four billion, six hundred sixty-nine million, seven hundred six thousand, two hundred forty".