665904081 has 4 divisors (see below), whose sum is σ = 887872112. Its totient is φ = 443936052.

The previous prime is 665904079. The next prime is 665904097. The reversal of 665904081 is 180409566.

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 not a de Polignac number, because 665904081 - 2¹ = 665904079 is a prime.

It is a super-2 number, since 2×665904081² = 886856490184909122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665904011) 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, 110984011 + ... + 110984016.

It is an arithmetic number, because the mean of its divisors is an integer number (221968028).

Almost surely, 2^665904081 is an apocalyptic number.

It is an amenable number.

665904081 is a deficient number, since it is larger than the sum of its proper divisors (221968031).

665904081 is a wasteful number, since it uses less digits than its factorization.

665904081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221968030.

The product of its (nonzero) digits is 51840, while the sum is 39.

The square root of 665904081 is about 25805.1173413337. The cubic root of 665904081 is about 873.2472476802.

The spelling of 665904081 in words is "six hundred sixty-five million, nine hundred four thousand, eighty-one".