668809 has 4 divisors (see below), whose sum is σ = 671616. Its totient is φ = 666004.

The previous prime is 668803. The next prime is 668813. The reversal of 668809 is 908866.

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 668809 - 2¹³ = 660617 is a prime.

It is a Duffinian number.

668809 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (668803) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1009 + ... + 1534.

It is an arithmetic number, because the mean of its divisors is an integer number (167904).

2⁶⁶⁸⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

668809 is a deficient number, since it is larger than the sum of its proper divisors (2807).

668809 is a wasteful number, since it uses less digits than its factorization.

668809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2806.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 668809 is about 817.8074345468. The cubic root of 668809 is about 87.4515214452.

The spelling of 668809 in words is "six hundred sixty-eight thousand, eight hundred nine".