644586768 has 240 divisors, whose sum is σ = 2213132160. Its totient is φ = 178972416.

The previous prime is 644586763. The next prime is 644586797. The reversal of 644586768 is 867685446.

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

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

It is not an unprimeable number, because it can be changed into a prime (644586763) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 782805 + ... + 783627.

It is an arithmetic number, because the mean of its divisors is an integer number (9221384).

Almost surely, 2^644586768 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644586768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1106566080).

644586768 is an abundant number, since it is smaller than the sum of its proper divisors (1568545392).

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

644586768 is a wasteful number, since it uses less digits than its factorization.

644586768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 891 (or 872 counting only the distinct ones).

The product of its digits is 7741440, while the sum is 54.

The square root of 644586768 is about 25388.7133978861. The cubic root of 644586768 is about 863.8277048415.

The spelling of 644586768 in words is "six hundred forty-four million, five hundred eighty-six thousand, seven hundred sixty-eight".