665617121665 has 16 divisors (see below), whose sum is σ = 837418513536. Its totient is φ = 506927836800.

The previous prime is 665617121639. The next prime is 665617121683. The reversal of 665617121665 is 566121716566.

It is not a de Polignac number, because 665617121665 - 2²⁹ = 665080250753 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13691316 + ... + 13739845.

It is an arithmetic number, because the mean of its divisors is an integer number (52338657096).

Almost surely, 2^665617121665 is an apocalyptic number.

It is an amenable number.

665617121665 is a deficient number, since it is larger than the sum of its proper divisors (171801391871).

665617121665 is a wasteful number, since it uses less digits than its factorization.

665617121665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27431400.

The product of its digits is 2721600, while the sum is 52.

The spelling of 665617121665 in words is "six hundred sixty-five billion, six hundred seventeen million, one hundred twenty-one thousand, six hundred sixty-five".