665011261 has 4 divisors (see below), whose sum is σ = 665224672. Its totient is φ = 664797852.

The previous prime is 665011231. The next prime is 665011271. The reversal of 665011261 is 162110566.

665011261 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 665011261 - 2⁷ = 665011133 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 (665011231) 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, 101961 + ... + 108286.

It is an arithmetic number, because the mean of its divisors is an integer number (166306168).

Almost surely, 2^665011261 is an apocalyptic number.

It is an amenable number.

665011261 is a deficient number, since it is larger than the sum of its proper divisors (213411).

665011261 is a wasteful number, since it uses less digits than its factorization.

665011261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213410.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 665011261 is about 25787.8122569558. The cubic root of 665011261 is about 872.8568004005.

The spelling of 665011261 in words is "six hundred sixty-five million, eleven thousand, two hundred sixty-one".