66600656561 has 4 divisors (see below), whose sum is σ = 66601206000. Its totient is φ = 66600107124.

The previous prime is 66600656539. The next prime is 66600656569. The reversal of 66600656561 is 16565600666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 66600656561 - 2⁶ = 66600656497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66600656569) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3911 + ... + 364988.

It is an arithmetic number, because the mean of its divisors is an integer number (16650301500).

Almost surely, 2^66600656561 is an apocalyptic number.

It is an amenable number.

66600656561 is a deficient number, since it is larger than the sum of its proper divisors (549439).

66600656561 is a wasteful number, since it uses less digits than its factorization.

66600656561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 549438.

The product of its (nonzero) digits is 1166400, while the sum is 47.

The spelling of 66600656561 in words is "sixty-six billion, six hundred million, six hundred fifty-six thousand, five hundred sixty-one".