666601881 has 8 divisors (see below), whose sum is σ = 969602784. Its totient is φ = 404001120.

The previous prime is 666601877. The next prime is 666601913. The reversal of 666601881 is 188106666.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 666601881 - 2² = 666601877 is a prime.

It is a super-2 number, since 2×666601881² = 888716135505476322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (666601861) 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 7 ways as a sum of consecutive naturals, for example, 10099996 + ... + 10100061.

It is an arithmetic number, because the mean of its divisors is an integer number (121200348).

Almost surely, 2^666601881 is an apocalyptic number.

It is an amenable number.

666601881 is a deficient number, since it is larger than the sum of its proper divisors (303000903).

666601881 is a wasteful number, since it uses less digits than its factorization.

666601881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20200071.

The product of its (nonzero) digits is 82944, while the sum is 42.

The square root of 666601881 is about 25818.6343751950. The cubic root of 666601881 is about 873.5521660732.

The spelling of 666601881 in words is "six hundred sixty-six million, six hundred one thousand, eight hundred eighty-one".