1666768781827 has 4 divisors (see below), whose sum is σ = 1666778546920. Its totient is φ = 1666759016736.

The previous prime is 1666768781801. The next prime is 1666768781833. The reversal of 1666768781827 is 7281878676661.

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

It is a cyclic number.

It is not a de Polignac number, because 1666768781827 - 2¹⁵ = 1666768749059 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1666768781827.

It is not an unprimeable number, because it can be changed into a prime (1666768781857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4621878 + ... + 4969435.

It is an arithmetic number, because the mean of its divisors is an integer number (416694636730).

Almost surely, 2^{1666768781827} is an apocalyptic number.

1666768781827 is a deficient number, since it is larger than the sum of its proper divisors (9765093).

1666768781827 is an equidigital number, since it uses as much as digits as its factorization.

1666768781827 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9765092.

The product of its digits is 455196672, while the sum is 73.

The spelling of 1666768781827 in words is "one trillion, six hundred sixty-six billion, seven hundred sixty-eight million, seven hundred eighty-one thousand, eight hundred twenty-seven".