1666254526661 has 4 divisors (see below), whose sum is σ = 1666273233324. Its totient is φ = 1666235820000.

The previous prime is 1666254526633. The next prime is 1666254526663.

1666254526661 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 1033424730625 + 632829796036 = 1016575^2 + 795506^2 .

It is a cyclic number.

It is not a de Polignac number, because 1666254526661 - 2³⁰ = 1665180784837 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1666254526597 and 1666254526606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666254526663) 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, 9219080 + ... + 9398081.

It is an arithmetic number, because the mean of its divisors is an integer number (416568308331).

Almost surely, 2^{1666254526661} is an apocalyptic number.

It is an amenable number.

1666254526661 is a deficient number, since it is larger than the sum of its proper divisors (18706663).

1666254526661 is an equidigital number, since it uses as much as digits as its factorization.

1666254526661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18706662.

The product of its digits is 18662400, while the sum is 56.

The spelling of 1666254526661 in words is "one trillion, six hundred sixty-six billion, two hundred fifty-four million, five hundred twenty-six thousand, six hundred sixty-one".