1666638018243 has 80 divisors (see below), whose sum is σ = 2743551119232. Its totient is φ = 999861408000.

The previous prime is 1666638018203. The next prime is 1666638018263. The reversal of 1666638018243 is 3428108366661.

It is not a de Polignac number, because 1666638018243 - 2¹⁷ = 1666637887171 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1666638018243.

It is not an unprimeable number, because it can be changed into a prime (1666638018203) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 81643708 + ... + 81664118.

Almost surely, 2^{1666638018243} is an apocalyptic number.

1666638018243 is a deficient number, since it is larger than the sum of its proper divisors (1076913100989).

1666638018243 is a wasteful number, since it uses less digits than its factorization.

1666638018243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21358 (or 21349 counting only the distinct ones).

The product of its (nonzero) digits is 5971968, while the sum is 54.

The spelling of 1666638018243 in words is "one trillion, six hundred sixty-six billion, six hundred thirty-eight million, eighteen thousand, two hundred forty-three".