66440209 has 4 divisors (see below), whose sum is σ = 72480240. Its totient is φ = 60400180.

The previous prime is 66440201. The next prime is 66440237. The reversal of 66440209 is 90204466.

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 66440209 - 2³ = 66440201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66440201) 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, 3019999 + ... + 3020020.

It is an arithmetic number, because the mean of its divisors is an integer number (18120060).

Almost surely, 2^66440209 is an apocalyptic number.

It is an amenable number.

66440209 is a deficient number, since it is larger than the sum of its proper divisors (6040031).

66440209 is a wasteful number, since it uses less digits than its factorization.

66440209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6040030.

The product of its (nonzero) digits is 10368, while the sum is 31.

The square root of 66440209 is about 8151.0863693130. The cubic root of 66440209 is about 405.0204917742.

The spelling of 66440209 in words is "sixty-six million, four hundred forty thousand, two hundred nine".