665686686566 has 16 divisors (see below), whose sum is σ = 1103094167040. Its totient is φ = 298754668680.

The previous prime is 665686686563. The next prime is 665686686617.

665686686566 is nontrivially palindromic in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 665686686493 and 665686686502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665686686563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 191507666 + ... + 191511141.

It is an arithmetic number, because the mean of its divisors is an integer number (68943385440).

Almost surely, 2^665686686566 is an apocalyptic number.

665686686566 is a deficient number, since it is larger than the sum of its proper divisors (437407480474).

665686686566 is a wasteful number, since it uses less digits than its factorization.

665686686566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 383018899.

The product of its digits is 2687385600, while the sum is 74.

The spelling of 665686686566 in words is "six hundred sixty-five billion, six hundred eighty-six million, six hundred eighty-six thousand, five hundred sixty-six".