66666665640 has 128 divisors (see below), whose sum is σ = 208785807360. Its totient is φ = 16997485824.

The previous prime is 66666665633. The next prime is 66666665641. The reversal of 66666665640 is 4656666666.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (66666665641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9565437 + ... + 9572403.

It is an arithmetic number, because the mean of its divisors is an integer number (1631139120).

Almost surely, 2^66666665640 is an apocalyptic number.

66666665640 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 66666665640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (104392903680).

66666665640 is an abundant number, since it is smaller than the sum of its proper divisors (142119141720).

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

66666665640 is a wasteful number, since it uses less digits than its factorization.

66666665640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10471 (or 10467 counting only the distinct ones).

The product of its (nonzero) digits is 33592320, while the sum is 57.

The spelling of 66666665640 in words is "sixty-six billion, six hundred sixty-six million, six hundred sixty-five thousand, six hundred forty".