1661566565605 has 8 divisors (see below), whose sum is σ = 1993916916864. Its totient is φ = 1329228560400.

The previous prime is 1661566565543. The next prime is 1661566565647. The reversal of 1661566565605 is 5065656651661.

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

It is a de Polignac number, because none of the positive numbers 2^k-1661566565605 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 1661566565605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2787801 + ... + 3330910.

It is an arithmetic number, because the mean of its divisors is an integer number (249239614608).

Almost surely, 2^{1661566565605} is an apocalyptic number.

It is an amenable number.

1661566565605 is a deficient number, since it is larger than the sum of its proper divisors (332350351259).

1661566565605 is an equidigital number, since it uses as much as digits as its factorization.

1661566565605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6173027.

The product of its (nonzero) digits is 29160000, while the sum is 58.

The spelling of 1661566565605 in words is "one trillion, six hundred sixty-one billion, five hundred sixty-six million, five hundred sixty-five thousand, six hundred five".