66678687666 has 144 divisors (see below), whose sum is σ = 156112220160. Its totient is φ = 20560055040.

The previous prime is 66678687661. The next prime is 66678687749.

It is a happy number.

66678687666 is nontrivially palindromic in base 10.

66678687666 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 66678687594 and 66678687603.

It is not an unprimeable number, because it can be changed into a prime (66678687661) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 52132815 + ... + 52134093.

It is an arithmetic number, because the mean of its divisors is an integer number (1084112640).

Almost surely, 2^66678687666 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66678687666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (78056110080).

66678687666 is an abundant number, since it is smaller than the sum of its proper divisors (89433532494).

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

66678687666 is a wasteful number, since it uses less digits than its factorization.

66678687666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1509 (or 1487 counting only the distinct ones).

The product of its digits is 877879296, while the sum is 72.

The spelling of 66678687666 in words is "sixty-six billion, six hundred seventy-eight million, six hundred eighty-seven thousand, six hundred sixty-six".