666591515 has 4 divisors (see below), whose sum is σ = 799909824. Its totient is φ = 533273208.

The previous prime is 666591503. The next prime is 666591517. The reversal of 666591515 is 515195666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 515195666 = 2 ⋅257597833.

It is a cyclic number.

It is not a de Polignac number, because 666591515 - 2⁸ = 666591259 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666591517) 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, 66659147 + ... + 66659156.

It is an arithmetic number, because the mean of its divisors is an integer number (199977456).

Almost surely, 2^666591515 is an apocalyptic number.

666591515 is a deficient number, since it is larger than the sum of its proper divisors (133318309).

666591515 is a wasteful number, since it uses less digits than its factorization.

666591515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133318308.

The product of its digits is 243000, while the sum is 44.

The square root of 666591515 is about 25818.4336279334. The cubic root of 666591515 is about 873.5476379888.

The spelling of 666591515 in words is "six hundred sixty-six million, five hundred ninety-one thousand, five hundred fifteen".