666212661 has 32 divisors (see below), whose sum is σ = 1021363200. Its totient is φ = 428742720.

The previous prime is 666212653. The next prime is 666212669. The reversal of 666212661 is 166212666.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (666212653) and next prime (666212669).

It is not a de Polignac number, because 666212661 - 2³ = 666212653 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666212669) 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 31 ways as a sum of consecutive naturals, for example, 465495 + ... + 466923.

It is an arithmetic number, because the mean of its divisors is an integer number (31917600).

Almost surely, 2^666212661 is an apocalyptic number.

It is an amenable number.

666212661 is a deficient number, since it is larger than the sum of its proper divisors (355150539).

666212661 is a wasteful number, since it uses less digits than its factorization.

666212661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2026 (or 2020 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 666212661 is about 25811.0956954562. The cubic root of 666212661 is about 873.3821144628.

The spelling of 666212661 in words is "six hundred sixty-six million, two hundred twelve thousand, six hundred sixty-one".