666708509 has 4 divisors (see below), whose sum is σ = 669168960. Its totient is φ = 664248060.

The previous prime is 666708481. The next prime is 666708517. The reversal of 666708509 is 905807666.

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.

It is a cyclic number.

It is not a de Polignac number, because 666708509 - 2¹⁶ = 666642973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666708569) 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, 1229819 + ... + 1230360.

It is an arithmetic number, because the mean of its divisors is an integer number (167292240).

Almost surely, 2^666708509 is an apocalyptic number.

It is an amenable number.

666708509 is a deficient number, since it is larger than the sum of its proper divisors (2460451).

666708509 is a wasteful number, since it uses less digits than its factorization.

666708509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2460450.

The product of its (nonzero) digits is 544320, while the sum is 47.

The square root of 666708509 is about 25820.6992353034. The cubic root of 666708509 is about 873.5987406764.

The spelling of 666708509 in words is "six hundred sixty-six million, seven hundred eight thousand, five hundred nine".