138642809 has 8 divisors (see below), whose sum is σ = 142017408. Its totient is φ = 135286000.

The previous prime is 138642773. The next prime is 138642821. The reversal of 138642809 is 908246831.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 138642809 - 2¹⁶ = 138577273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138642209) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12059 + ... + 20559.

It is an arithmetic number, because the mean of its divisors is an integer number (17752176).

Almost surely, 2^138642809 is an apocalyptic number.

It is an amenable number.

138642809 is a deficient number, since it is larger than the sum of its proper divisors (3374599).

138642809 is an equidigital number, since it uses as much as digits as its factorization.

138642809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8895.

The product of its (nonzero) digits is 82944, while the sum is 41.

The square root of 138642809 is about 11774.6681057260. The cubic root of 138642809 is about 517.5660525426.

The spelling of 138642809 in words is "one hundred thirty-eight million, six hundred forty-two thousand, eight hundred nine".