1665611665605 has 12 divisors (see below), whose sum is σ = 2887060220460. Its totient is φ = 888326221632.

The previous prime is 1665611665591. The next prime is 1665611665631. The reversal of 1665611665605 is 5065661165661.

1665611665605 is a `hidden beast` number, since 1 + 6 + 6 + 5 + 6 + 11 + 66 + 560 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 638619944769 + 1026991720836 = 799137^2 + 1013406^2 .

It is not a de Polignac number, because 1665611665605 - 2¹⁰ = 1665611664581 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18506796240 + ... + 18506796329.

It is an arithmetic number, because the mean of its divisors is an integer number (240588351705).

Almost surely, 2^{1665611665605} is an apocalyptic number.

1665611665605 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1665611665605 is a deficient number, since it is larger than the sum of its proper divisors (1221448554855).

1665611665605 is a wasteful number, since it uses less digits than its factorization.

1665611665605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37013592580 (or 37013592577 counting only the distinct ones).

The product of its (nonzero) digits is 5832000, while the sum is 54.

The spelling of 1665611665605 in words is "one trillion, six hundred sixty-five billion, six hundred eleven million, six hundred sixty-five thousand, six hundred five".