660869809 has 4 divisors (see below), whose sum is σ = 661178916. Its totient is φ = 660560704.

The previous prime is 660869789. The next prime is 660869831. The reversal of 660869809 is 908968066.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 908968066 = 2 ⋅454484033.

It can be written as a sum of positive squares in 2 ways, for example, as 315950625 + 344919184 = 17775^2 + 18572^2 .

It is a cyclic number.

It is not a de Polignac number, because 660869809 - 2¹¹ = 660867761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (660869009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 151324 + ... + 155629.

It is an arithmetic number, because the mean of its divisors is an integer number (165294729).

Almost surely, 2^660869809 is an apocalyptic number.

It is an amenable number.

660869809 is a deficient number, since it is larger than the sum of its proper divisors (309107).

660869809 is a wasteful number, since it uses less digits than its factorization.

660869809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309106.

The product of its (nonzero) digits is 1119744, while the sum is 52.

The square root of 660869809 is about 25707.3882181757. The cubic root of 660869809 is about 871.0410794172.

The spelling of 660869809 in words is "six hundred sixty million, eight hundred sixty-nine thousand, eight hundred nine".