666509438784 has 224 divisors, whose sum is σ = 2086138494720. Its totient is φ = 183754948608.

The previous prime is 666509438747. The next prime is 666509438789. The reversal of 666509438784 is 487834905666.

It is a tau number, because it is divible by the number of its divisors (224).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666509438789) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 82352242 + ... + 82360334.

It is an arithmetic number, because the mean of its divisors is an integer number (9313118280).

Almost surely, 2^666509438784 is an apocalyptic number.

666509438784 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 666509438784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1043069247360).

666509438784 is an abundant number, since it is smaller than the sum of its proper divisors (1419629055936).

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

666509438784 is a wasteful number, since it uses less digits than its factorization.

666509438784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10257 (or 10247 counting only the distinct ones).

The product of its (nonzero) digits is 209018880, while the sum is 66.

The spelling of 666509438784 in words is "six hundred sixty-six billion, five hundred nine million, four hundred thirty-eight thousand, seven hundred eighty-four".