16666666661 has 8 divisors (see below), whose sum is σ = 16731867648. Its totient is φ = 16601508000.

The previous prime is 16666666631. The next prime is 16666666697.

16666666661 = 7561² + 7562² + ... + 7841².

It is a happy number.

16666666661 is nontrivially palindromic in base 10.

16666666661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 16666666661 - 2²⁶ = 16599557797 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 16666666597 and 16666666606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16666666631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 944126 + ... + 961616.

It is an arithmetic number, because the mean of its divisors is an integer number (2091483456).

Almost surely, 2^16666666661 is an apocalyptic number.

It is an amenable number.

16666666661 is a deficient number, since it is larger than the sum of its proper divisors (65200987).

16666666661 is a wasteful number, since it uses less digits than its factorization.

16666666661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21163.

The product of its digits is 10077696, while the sum is 56.

The spelling of 16666666661 in words is "sixteen billion, six hundred sixty-six million, six hundred sixty-six thousand, six hundred sixty-one".