666171561 has 16 divisors (see below), whose sum is σ = 989595648. Its totient is φ = 395149200.

The previous prime is 666171551. The next prime is 666171587. The reversal of 666171561 is 165171666.

It is not a de Polignac number, because 666171561 - 2¹⁰ = 666170537 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (666171551) 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 in 15 ways as a sum of consecutive naturals, for example, 213205 + ... + 216306.

It is an arithmetic number, because the mean of its divisors is an integer number (61849728).

Almost surely, 2^666171561 is an apocalyptic number.

It is an amenable number.

666171561 is a deficient number, since it is larger than the sum of its proper divisors (323424087).

666171561 is a wasteful number, since it uses less digits than its factorization.

666171561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 429572.

The product of its digits is 45360, while the sum is 39.

The square root of 666171561 is about 25810.2995139537. The cubic root of 666171561 is about 873.3641538599.

The spelling of 666171561 in words is "six hundred sixty-six million, one hundred seventy-one thousand, five hundred sixty-one".