138509999 has 4 divisors (see below), whose sum is σ = 146657664. Its totient is φ = 130362336.

The previous prime is 138509957. The next prime is 138510007. The reversal of 138509999 is 999905831.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 999905831 = 347 ⋅2881573.

It is a cyclic number.

It is not a de Polignac number, because 138509999 - 2⁸ = 138509743 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 138509999.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138509909) 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, 4073807 + ... + 4073840.

It is an arithmetic number, because the mean of its divisors is an integer number (36664416).

Almost surely, 2^138509999 is an apocalyptic number.

138509999 is a deficient number, since it is larger than the sum of its proper divisors (8147665).

138509999 is an equidigital number, since it uses as much as digits as its factorization.

138509999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8147664.

The product of its (nonzero) digits is 787320, while the sum is 53.

The square root of 138509999 is about 11769.0271050754. The cubic root of 138509999 is about 517.4007358599.

The spelling of 138509999 in words is "one hundred thirty-eight million, five hundred nine thousand, nine hundred ninety-nine".