1666339035521 has 4 divisors (see below), whose sum is σ = 1666544333652. Its totient is φ = 1666133737392.

The previous prime is 1666339035469. The next prime is 1666339035523. The reversal of 1666339035521 is 1255309336661.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1261634400625 + 404704634896 = 1123225^2 + 636164^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1666339035521 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1666339035521.

It is not an unprimeable number, because it can be changed into a prime (1666339035523) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 102636890 + ... + 102653123.

It is an arithmetic number, because the mean of its divisors is an integer number (416636083413).

Almost surely, 2^{1666339035521} is an apocalyptic number.

It is an amenable number.

1666339035521 is a deficient number, since it is larger than the sum of its proper divisors (205298131).

1666339035521 is an equidigital number, since it uses as much as digits as its factorization.

1666339035521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205298130.

The product of its (nonzero) digits is 2624400, while the sum is 50.

The spelling of 1666339035521 in words is "one trillion, six hundred sixty-six billion, three hundred thirty-nine million, thirty-five thousand, five hundred twenty-one".