66681664 has 56 divisors (see below), whose sum is σ = 152083008. Its totient is φ = 28416000.

The previous prime is 66681653. The next prime is 66681677. The reversal of 66681664 is 46618666.

It is a tau number, because it is divible by the number of its divisors (56).

It is a self number, because there is not a number n which added to its sum of digits gives 66681664.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 112152 + ... + 112744.

It is an arithmetic number, because the mean of its divisors is an integer number (2715768).

Almost surely, 2^66681664 is an apocalyptic number.

66681664 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 66681664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (76041504).

66681664 is an abundant number, since it is smaller than the sum of its proper divisors (85401344).

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

66681664 is a wasteful number, since it uses less digits than its factorization.

66681664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 863 (or 853 counting only the distinct ones).

The product of its digits is 248832, while the sum is 43.

The square root of 66681664 is about 8165.8841529867. The cubic root of 66681664 is about 405.5105363621.

The spelling of 66681664 in words is "sixty-six million, six hundred eighty-one thousand, six hundred sixty-four".