644610891960 has 768 divisors, whose sum is σ = 2606970562560. Its totient is φ = 140060067840.

The previous prime is 644610891929. The next prime is 644610891973. The reversal of 644610891960 is 69198016446.

It is a happy number.

644610891960 is a `hidden beast` number, since 6 + 4 + 4 + 610 + 8 + 9 + 19 + 6 + 0 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 644610891897 and 644610891906.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 270729970 + ... + 270732350.

It is an arithmetic number, because the mean of its divisors is an integer number (3394492920).

Almost surely, 2^644610891960 is an apocalyptic number.

644610891960 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 644610891960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1303485281280).

644610891960 is an abundant number, since it is smaller than the sum of its proper divisors (1962359670600).

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

644610891960 is a wasteful number, since it uses less digits than its factorization.

644610891960 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2610 (or 2594 counting only the distinct ones).

The product of its (nonzero) digits is 2239488, while the sum is 54.

The spelling of 644610891960 in words is "six hundred forty-four billion, six hundred ten million, eight hundred ninety-one thousand, nine hundred sixty".