66666656 has 144 divisors (see below), whose sum is σ = 168317352. Its totient is φ = 25804800.

The previous prime is 66666653. The next prime is 66666667. The reversal of 66666656 is 65666666.

It can be written as a sum of positive squares in 4 ways, for example, as 30426256 + 36240400 = 5516^2 + 6020^2 .

Its product of digits (1399680) is a multiple of the sum of its prime divisors (128).

It is a self number, because there is not a number n which added to its sum of digits gives 66666656.

It is not an unprimeable number, because it can be changed into a prime (66666653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1092866 + ... + 1092926.

Almost surely, 2^66666656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66666656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (84158676).

66666656 is an abundant number, since it is smaller than the sum of its proper divisors (101650696).

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

66666656 is a wasteful number, since it uses less digits than its factorization.

66666656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143 (or 128 counting only the distinct ones).

The product of its digits is 1399680, while the sum is 47.

The square root of 66666656 is about 8164.9651560800. The cubic root of 66666656 is about 405.4801114126.

The spelling of 66666656 in words is "sixty-six million, six hundred sixty-six thousand, six hundred fifty-six".