66538309 has 4 divisors (see below), whose sum is σ = 67184416. Its totient is φ = 65892204.

The previous prime is 66538279. The next prime is 66538313. The reversal of 66538309 is 90383566.

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 66538309 - 2⁹ = 66537797 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 (66538009) 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, 322899 + ... + 323104.

It is an arithmetic number, because the mean of its divisors is an integer number (16796104).

Almost surely, 2^66538309 is an apocalyptic number.

It is an amenable number.

66538309 is a deficient number, since it is larger than the sum of its proper divisors (646107).

66538309 is a wasteful number, since it uses less digits than its factorization.

66538309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 646106.

The product of its (nonzero) digits is 116640, while the sum is 40.

The square root of 66538309 is about 8157.1017524609. The cubic root of 66538309 is about 405.2197334264.

The spelling of 66538309 in words is "sixty-six million, five hundred thirty-eight thousand, three hundred nine".