666666081 has 12 divisors (see below), whose sum is σ = 969426900. Its totient is φ = 441460320.

The previous prime is 666666079. The next prime is 666666083. The reversal of 666666081 is 180666666.

It is an interprime number because it is at equal distance from previous prime (666666079) and next prime (666666083).

It can be written as a sum of positive squares in 2 ways, for example, as 268304400 + 398361681 = 16380^2 + 19959^2 .

It is not a de Polignac number, because 666666081 - 2¹ = 666666079 is a prime.

It is a super-2 number, since 2×666666081² = 888887327111797122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (666666083) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 247230 + ... + 249911.

It is an arithmetic number, because the mean of its divisors is an integer number (80785575).

Almost surely, 2^666666081 is an apocalyptic number.

It is an amenable number.

666666081 is a deficient number, since it is larger than the sum of its proper divisors (302760819).

666666081 is a wasteful number, since it uses less digits than its factorization.

666666081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 497296 (or 497293 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 666666081 is about 25819.8776333274. The cubic root of 666666081 is about 873.5802089227.

The spelling of 666666081 in words is "six hundred sixty-six million, six hundred sixty-six thousand, eighty-one".