666430181 has 2 divisors, whose sum is σ = 666430182. Its totient is φ = 666430180.

The previous prime is 666430159. The next prime is 666430217. The reversal of 666430181 is 181034666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 512297956 + 154132225 = 22634^2 + 12415^2 .

It is a cyclic number.

It is not a de Polignac number, because 666430181 - 2⁶ = 666430117 is a prime.

It is a super-2 number, since 2×666430181² = 888258372295385522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666430781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333215090 + 333215091.

It is an arithmetic number, because the mean of its divisors is an integer number (333215091).

Almost surely, 2^666430181 is an apocalyptic number.

It is an amenable number.

666430181 is a deficient number, since it is larger than the sum of its proper divisors (1).

666430181 is an equidigital number, since it uses as much as digits as its factorization.

666430181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 35.

The square root of 666430181 is about 25815.3090432790. The cubic root of 666430181 is about 873.4771578907.

The spelling of 666430181 in words is "six hundred sixty-six million, four hundred thirty thousand, one hundred eighty-one".