66209639 has 4 divisors (see below), whose sum is σ = 68492760. Its totient is φ = 63926520.

The previous prime is 66209621. The next prime is 66209651. The reversal of 66209639 is 93690266.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 66209639 - 2¹⁶ = 66144103 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 66209596 and 66209605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66209609) 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, 1141517 + ... + 1141574.

It is an arithmetic number, because the mean of its divisors is an integer number (17123190).

Almost surely, 2^66209639 is an apocalyptic number.

66209639 is a deficient number, since it is larger than the sum of its proper divisors (2283121).

66209639 is a wasteful number, since it uses less digits than its factorization.

66209639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2283120.

The product of its (nonzero) digits is 104976, while the sum is 41.

The square root of 66209639 is about 8136.9305637937. The cubic root of 66209639 is about 404.5514293823.

The spelling of 66209639 in words is "sixty-six million, two hundred nine thousand, six hundred thirty-nine".