66581816872 has 8 divisors (see below), whose sum is σ = 124840906650. Its totient is φ = 33290908432.

The previous prime is 66581816863. The next prime is 66581816879. The reversal of 66581816872 is 27861818566.

It can be written as a sum of positive squares in only one way, i.e., 48279515076 + 18302301796 = 219726^2 + 135286^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (66581816879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4161363547 + ... + 4161363562.

Almost surely, 2^66581816872 is an apocalyptic number.

It is an amenable number.

66581816872 is a deficient number, since it is larger than the sum of its proper divisors (58259089778).

66581816872 is a wasteful number, since it uses less digits than its factorization.

66581816872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8322727115 (or 8322727111 counting only the distinct ones).

The product of its digits is 7741440, while the sum is 58.

The spelling of 66581816872 in words is "sixty-six billion, five hundred eighty-one million, eight hundred sixteen thousand, eight hundred seventy-two".