665304061221 has 24 divisors (see below), whose sum is σ = 1021890968280. Its totient is φ = 415654050816.

The previous prime is 665304061217. The next prime is 665304061231. The reversal of 665304061221 is 122160403566.

665304061221 is a `hidden beast` number, since 6 + 6 + 5 + 30 + 4 + 0 + 612 + 2 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 23558873121 + 641745188100 = 153489^2 + 801090^2 .

It is not a de Polignac number, because 665304061221 - 2² = 665304061217 is a prime.

It is a super-2 number, since 2×665304061221² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665304061231) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9295666 + ... + 9366963.

It is an arithmetic number, because the mean of its divisors is an integer number (42578790345).

Almost surely, 2^665304061221 is an apocalyptic number.

It is an amenable number.

665304061221 is a deficient number, since it is larger than the sum of its proper divisors (356586907059).

665304061221 is a wasteful number, since it uses less digits than its factorization.

665304061221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18662885 (or 18662882 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

Adding to 665304061221 its reverse (122160403566), we get a palindrome (787464464787).

The spelling of 665304061221 in words is "six hundred sixty-five billion, three hundred four million, sixty-one thousand, two hundred twenty-one".