666017021 has 4 divisors (see below), whose sum is σ = 666154944. Its totient is φ = 665879100.

The previous prime is 666017017. The next prime is 666017039. The reversal of 666017021 is 120710666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 120710666 = 2 ⋅60355333.

It is a cyclic number.

It is not a de Polignac number, because 666017021 - 2² = 666017017 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666017071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61445 + ... + 71466.

It is an arithmetic number, because the mean of its divisors is an integer number (166538736).

Almost surely, 2^666017021 is an apocalyptic number.

It is an amenable number.

666017021 is a deficient number, since it is larger than the sum of its proper divisors (137923).

666017021 is a wasteful number, since it uses less digits than its factorization.

666017021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137922.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 666017021 is about 25807.3055741974. The cubic root of 666017021 is about 873.2966136333.

Adding to 666017021 its reverse (120710666), we get a palindrome (786727687).

The spelling of 666017021 in words is "six hundred sixty-six million, seventeen thousand, twenty-one".