665106352452221 has 4 divisors (see below), whose sum is σ = 686561396079744. Its totient is φ = 643651308824700.

The previous prime is 665106352452169. The next prime is 665106352452257. The reversal of 665106352452221 is 122254253601566.

It is a happy number.

665106352452221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 665106352452221 - 2³⁴ = 665089172583037 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 665106352452221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665106352452281) 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, 10727521813715 + ... + 10727521813776.

It is an arithmetic number, because the mean of its divisors is an integer number (171640349019936).

Almost surely, 2^{665106352452221} is an apocalyptic number.

It is an amenable number.

665106352452221 is a deficient number, since it is larger than the sum of its proper divisors (21455043627523).

665106352452221 is a wasteful number, since it uses less digits than its factorization.

665106352452221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21455043627522.

The product of its (nonzero) digits is 5184000, while the sum is 50.

The spelling of 665106352452221 in words is "six hundred sixty-five trillion, one hundred six billion, three hundred fifty-two million, four hundred fifty-two thousand, two hundred twenty-one".