665809532881 has 4 divisors (see below), whose sum is σ = 665986566564. Its totient is φ = 665632499200.

The previous prime is 665809532749. The next prime is 665809532923. The reversal of 665809532881 is 188235908566.

It is a happy number.

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 435256867600 + 230552665281 = 659740^2 + 480159^2 .

It is a cyclic number.

It is not a de Polignac number, because 665809532881 - 2¹³ = 665809524689 is a prime.

It is a super-2 number, since 2×665809532881² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665809502881) 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, 88511200 + ... + 88518721.

It is an arithmetic number, because the mean of its divisors is an integer number (166496641641).

Almost surely, 2^665809532881 is an apocalyptic number.

It is an amenable number.

665809532881 is a deficient number, since it is larger than the sum of its proper divisors (177033683).

665809532881 is a wasteful number, since it uses less digits than its factorization.

665809532881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177033682.

The product of its (nonzero) digits is 24883200, while the sum is 61.

The spelling of 665809532881 in words is "six hundred sixty-five billion, eight hundred nine million, five hundred thirty-two thousand, eight hundred eighty-one".