644966784 has 288 divisors, whose sum is σ = 2334979920. Its totient is φ = 167270400.

The previous prime is 644966767. The next prime is 644966797. The reversal of 644966784 is 487669446.

It is a tau number, because it is divible by the number of its divisors (288).

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 644966784.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 975414 + ... + 976074.

Almost surely, 2^644966784 is an apocalyptic number.

644966784 is a gapful number since it is divisible by the number (64) 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 644966784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1167489960).

644966784 is an abundant number, since it is smaller than the sum of its proper divisors (1690013136).

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

644966784 is a wasteful number, since it uses less digits than its factorization.

644966784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 710 (or 684 counting only the distinct ones).

The product of its digits is 6967296, while the sum is 54.

The square root of 644966784 is about 25396.1962506199. The cubic root of 644966784 is about 863.9974279759.

The spelling of 644966784 in words is "six hundred forty-four million, nine hundred sixty-six thousand, seven hundred eighty-four".