66006511661 has 4 divisors (see below), whose sum is σ = 68282598300. Its totient is φ = 63730425024.

The previous prime is 66006511607. The next prime is 66006511673. The reversal of 66006511661 is 16611560066.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 35876148100 + 30130363561 = 189410^2 + 173581^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66006511661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66006541661) 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, 1138043276 + ... + 1138043333.

It is an arithmetic number, because the mean of its divisors is an integer number (17070649575).

Almost surely, 2^66006511661 is an apocalyptic number.

It is an amenable number.

66006511661 is a deficient number, since it is larger than the sum of its proper divisors (2276086639).

66006511661 is a wasteful number, since it uses less digits than its factorization.

66006511661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2276086638.

The product of its (nonzero) digits is 38880, while the sum is 38.

The spelling of 66006511661 in words is "sixty-six billion, six million, five hundred eleven thousand, six hundred sixty-one".