66638683666 has 4 divisors (see below), whose sum is σ = 99958025502. Its totient is φ = 33319341832.

The previous prime is 66638683607. The next prime is 66638683691.

66638683666 is nontrivially palindromic in base 10.

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

It can be written as a sum of positive squares in only one way, i.e., 45896635225 + 20742048441 = 214235^2 + 144021^2 .

It is a junction number, because it is equal to n+sod(n) for n = 66638683598 and 66638683607.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16659670915 + ... + 16659670918.

Almost surely, 2^66638683666 is an apocalyptic number.

66638683666 is a deficient number, since it is larger than the sum of its proper divisors (33319341836).

66638683666 is a wasteful number, since it uses less digits than its factorization.

66638683666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33319341835.

The product of its digits is 161243136, while the sum is 64.

The spelling of 66638683666 in words is "sixty-six billion, six hundred thirty-eight million, six hundred eighty-three thousand, six hundred sixty-six".