666975581 has 4 divisors (see below), whose sum is σ = 668461500. Its totient is φ = 665489664.

The previous prime is 666975539. The next prime is 666975593. The reversal of 666975581 is 185579666.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 140043556 + 526932025 = 11834^2 + 22955^2 .

It is a cyclic number.

It is not a de Polignac number, because 666975581 - 2¹⁰ = 666974557 is a prime.

It is a super-2 number, since 2×666975581² = 889712851300575122, which contains 22 as substring.

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 (666975521) 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 3 ways as a sum of consecutive naturals, for example, 742286 + ... + 743183.

It is an arithmetic number, because the mean of its divisors is an integer number (167115375).

Almost surely, 2^666975581 is an apocalyptic number.

It is an amenable number.

666975581 is a deficient number, since it is larger than the sum of its proper divisors (1485919).

666975581 is a wasteful number, since it uses less digits than its factorization.

666975581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1485918.

The product of its digits is 2721600, while the sum is 53.

The square root of 666975581 is about 25825.8703822349. The cubic root of 666975581 is about 873.7153746641.

The spelling of 666975581 in words is "six hundred sixty-six million, nine hundred seventy-five thousand, five hundred eighty-one".