1668138318661 has 4 divisors (see below), whose sum is σ = 1668331376524. Its totient is φ = 1667945260800.

The previous prime is 1668138318653. The next prime is 1668138318673.

1668138318661 is nontrivially palindromic in base 10.

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 271238889636 + 1396899429025 = 520806^2 + 1181905^2 .

It is a cyclic number.

It is not a de Polignac number, because 1668138318661 - 2³ = 1668138318653 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1668138318596 and 1668138318605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1668138318461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 96515970 + ... + 96533251.

It is an arithmetic number, because the mean of its divisors is an integer number (417082844131).

Almost surely, 2^{1668138318661} is an apocalyptic number.

It is an amenable number.

1668138318661 is a deficient number, since it is larger than the sum of its proper divisors (193057863).

1668138318661 is an equidigital number, since it uses as much as digits as its factorization.

1668138318661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193057862.

The product of its digits is 5971968, while the sum is 58.

The spelling of 1668138318661 in words is "one trillion, six hundred sixty-eight billion, one hundred thirty-eight million, three hundred eighteen thousand, six hundred sixty-one".