666500161 has 2 divisors, whose sum is σ = 666500162. Its totient is φ = 666500160.

The previous prime is 666500137. The next prime is 666500179. The reversal of 666500161 is 161005666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 550183936 + 116316225 = 23456^2 + 10785^2 .

It is a cyclic number.

It is not a de Polignac number, because 666500161 - 2⁷ = 666500033 is a prime.

It is a super-2 number, since 2×666500161² = 888444929226051842, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (666503161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333250080 + 333250081.

It is an arithmetic number, because the mean of its divisors is an integer number (333250081).

Almost surely, 2^666500161 is an apocalyptic number.

It is an amenable number.

666500161 is a deficient number, since it is larger than the sum of its proper divisors (1).

666500161 is an equidigital number, since it uses as much as digits as its factorization.

666500161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 666500161 is about 25816.6644049924. The cubic root of 666500161 is about 873.5077306318.

The spelling of 666500161 in words is "six hundred sixty-six million, five hundred thousand, one hundred sixty-one".