1666661020517 has 8 divisors (see below), whose sum is σ = 1735703451000. Its totient is φ = 1598390014144.

The previous prime is 1666661020511. The next prime is 1666661020543. The reversal of 1666661020517 is 7150201666661.

It can be written as a sum of positive squares in 4 ways, for example, as 53217414721 + 1613443605796 = 230689^2 + 1270214^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1666661020517 - 2¹⁴ = 1666661004133 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666661020511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 192851618 + ... + 192860259.

It is an arithmetic number, because the mean of its divisors is an integer number (216962931375).

Almost surely, 2^{1666661020517} is an apocalyptic number.

It is an amenable number.

1666661020517 is a deficient number, since it is larger than the sum of its proper divisors (69042430483).

1666661020517 is a wasteful number, since it uses less digits than its factorization.

1666661020517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 385712055.

The product of its (nonzero) digits is 544320, while the sum is 47.

The spelling of 1666661020517 in words is "one trillion, six hundred sixty-six billion, six hundred sixty-one million, twenty thousand, five hundred seventeen".