665128277221 has 4 divisors (see below), whose sum is σ = 666494044192. Its totient is φ = 663762510252.

The previous prime is 665128277213. The next prime is 665128277257. The reversal of 665128277221 is 122772821566.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 665128277221 - 2³ = 665128277213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665128227221) 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, 682882755 + ... + 682883728.

It is an arithmetic number, because the mean of its divisors is an integer number (166623511048).

Almost surely, 2^665128277221 is an apocalyptic number.

It is an amenable number.

665128277221 is a deficient number, since it is larger than the sum of its proper divisors (1365766971).

665128277221 is a wasteful number, since it uses less digits than its factorization.

665128277221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1365766970.

The product of its digits is 1128960, while the sum is 49.

The spelling of 665128277221 in words is "six hundred sixty-five billion, one hundred twenty-eight million, two hundred seventy-seven thousand, two hundred twenty-one".