665181081 has 6 divisors (see below), whose sum is σ = 960817130. Its totient is φ = 443454048.

The previous prime is 665181067. The next prime is 665181103. The reversal of 665181081 is 180181566.

665181081 is a `hidden beast` number, since 66 + 518 + 1 + 0 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 528080400 + 137100681 = 22980^2 + 11709^2 .

It is not a de Polignac number, because 665181081 - 2⁶ = 665181017 is a prime.

It is a super-2 number, since 2×665181081² = 884931741040657122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665181031) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36954496 + ... + 36954513.

Almost surely, 2^665181081 is an apocalyptic number.

It is an amenable number.

665181081 is a deficient number, since it is larger than the sum of its proper divisors (295636049).

665181081 is a wasteful number, since it uses less digits than its factorization.

665181081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73909015 (or 73909012 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 665181081 is about 25791.1046874693. The cubic root of 665181081 is about 872.9310928398.

The spelling of 665181081 in words is "six hundred sixty-five million, one hundred eighty-one thousand, eighty-one".