644398917120 has 1280 divisors, whose sum is σ = 2775593779200. Its totient is φ = 138430218240.

The previous prime is 644398917109. The next prime is 644398917131. The reversal of 644398917120 is 21719893446.

644398917120 is a `hidden beast` number, since 6 + 4 + 439 + 89 + 1 + 7 + 120 = 666.

It is an interprime number because it is at equal distance from previous prime (644398917109) and next prime (644398917131).

It is a tau number, because it is divible by the number of its divisors (1280).

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (54).

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 127 ways as a sum of consecutive naturals, for example, 1755855177 + ... + 1755855543.

It is an arithmetic number, because the mean of its divisors is an integer number (2168432640).

Almost surely, 2^644398917120 is an apocalyptic number.

644398917120 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 644398917120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1387796889600).

644398917120 is an abundant number, since it is smaller than the sum of its proper divisors (2131194862080).

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

644398917120 is a wasteful number, since it uses less digits than its factorization.

644398917120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 616 (or 594 counting only the distinct ones).

The product of its (nonzero) digits is 2612736, while the sum is 54.

The spelling of 644398917120 in words is "six hundred forty-four billion, three hundred ninety-eight million, nine hundred seventeen thousand, one hundred twenty".