644238007776 has 432 divisors, whose sum is σ = 2102329442304. Its totient is φ = 186810624000.

The previous prime is 644238007723. The next prime is 644238007799. The reversal of 644238007776 is 677700832446.

644238007776 is a `hidden beast` number, since 6 + 4 + 423 + 80 + 0 + 77 + 76 = 666.

It is a super-2 number, since 2×644238007776² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 78647841 + ... + 78656031.

Almost surely, 2^644238007776 is an apocalyptic number.

644238007776 is a gapful number since it is divisible by the number (66) 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 644238007776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1051164721152).

644238007776 is an abundant number, since it is smaller than the sum of its proper divisors (1458091434528).

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

644238007776 is a wasteful number, since it uses less digits than its factorization.

644238007776 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8327 (or 8305 counting only the distinct ones).

The product of its (nonzero) digits is 9483264, while the sum is 54.

The spelling of 644238007776 in words is "six hundred forty-four billion, two hundred thirty-eight million, seven thousand, seven hundred seventy-six".