1666606666 has 4 divisors (see below), whose sum is σ = 2499910002. Its totient is φ = 833303332.

The previous prime is 1666606639. The next prime is 1666606687. The reversal of 1666606666 is 6666066661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6666066661 = 613 ⋅10874497.

It can be written as a sum of positive squares in only one way, i.e., 1495755625 + 170851041 = 38675^2 + 13071^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 416651665 + ... + 416651668.

Almost surely, 2^1666606666 is an apocalyptic number.

1666606666 is a deficient number, since it is larger than the sum of its proper divisors (833303336).

1666606666 is an equidigital number, since it uses as much as digits as its factorization.

1666606666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 833303335.

The product of its (nonzero) digits is 1679616, while the sum is 49.

The square root of 1666606666 is about 40824.0941846846. The cubic root of 1666606666 is about 1185.6168735946.

The spelling of 1666606666 in words is "one billion, six hundred sixty-six million, six hundred six thousand, six hundred sixty-six".