56691819666 has 24 divisors (see below), whose sum is σ = 123310232604. Its totient is φ = 18823741440.

The previous prime is 56691819659. The next prime is 56691819683. The reversal of 56691819666 is 66691819665.

It can be written as a sum of positive squares in 2 ways, for example, as 33013073025 + 23678746641 = 181695^2 + 153879^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6122895 + ... + 6132146.

Almost surely, 2^56691819666 is an apocalyptic number.

56691819666 is an abundant number, since it is smaller than the sum of its proper divisors (66618412938).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

56691819666 is a wasteful number, since it uses less digits than its factorization.

56691819666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12255306 (or 12255303 counting only the distinct ones).

The product of its digits is 25194240, while the sum is 63.

Subtracting 56691819666 from its reverse (66691819665), we obtain a palindrome (9999999999).

The spelling of 56691819666 in words is "fifty-six billion, six hundred ninety-one million, eight hundred nineteen thousand, six hundred sixty-six".