666698521 has 8 divisors (see below), whose sum is σ = 669468800. Its totient is φ = 663934320.

The previous prime is 666698519. The next prime is 666698533. The reversal of 666698521 is 125896666.

It is a happy number.

666698521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 666698521 - 2¹ = 666698519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666696521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 465835 + ... + 467263.

It is an arithmetic number, because the mean of its divisors is an integer number (83683600).

Almost surely, 2^666698521 is an apocalyptic number.

It is an amenable number.

666698521 is a deficient number, since it is larger than the sum of its proper divisors (2770279).

666698521 is a wasteful number, since it uses less digits than its factorization.

666698521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3039.

The product of its digits is 933120, while the sum is 49.

The square root of 666698521 is about 25820.5058238602. The cubic root of 666698521 is about 873.5943781764.

The spelling of 666698521 in words is "six hundred sixty-six million, six hundred ninety-eight thousand, five hundred twenty-one".