15661665565 has 32 divisors (see below), whose sum is σ = 24491738880. Its totient is φ = 9330177024.

The previous prime is 15661665541. The next prime is 15661665577. The reversal of 15661665565 is 56556616651.

It is not a de Polignac number, because 15661665565 - 2⁹ = 15661665053 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1004655 + ... + 1020124.

It is an arithmetic number, because the mean of its divisors is an integer number (765366840).

Almost surely, 2^15661665565 is an apocalyptic number.

It is an amenable number.

15661665565 is a deficient number, since it is larger than the sum of its proper divisors (8830073315).

15661665565 is a wasteful number, since it uses less digits than its factorization.

15661665565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2024821.

The product of its digits is 4860000, while the sum is 52.

The spelling of 15661665565 in words is "fifteen billion, six hundred sixty-one million, six hundred sixty-five thousand, five hundred sixty-five".