66565671561 has 16 divisors (see below), whose sum is σ = 98642603520. Its totient is φ = 44365057200.

The previous prime is 66565671527. The next prime is 66565671607. The reversal of 66565671561 is 16517656566.

66565671561 is a `hidden beast` number, since 6 + 6 + 5 + 6 + 5 + 6 + 71 + 561 = 666.

It is not a de Polignac number, because 66565671561 - 2¹⁰ = 66565670537 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 66565671498 and 66565671507.

It is not an unprimeable number, because it can be changed into a prime (66565672561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 233145 + ... + 432998.

It is an arithmetic number, because the mean of its divisors is an integer number (6165162720).

Almost surely, 2^66565671561 is an apocalyptic number.

It is an amenable number.

66565671561 is a deficient number, since it is larger than the sum of its proper divisors (32076931959).

66565671561 is a wasteful number, since it uses less digits than its factorization.

66565671561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 669853 (or 669847 counting only the distinct ones).

The product of its digits is 6804000, while the sum is 54.

The spelling of 66565671561 in words is "sixty-six billion, five hundred sixty-five million, six hundred seventy-one thousand, five hundred sixty-one".