138108991 has 8 divisors (see below), whose sum is σ = 146195280. Its totient is φ = 130244352.

The previous prime is 138108959. The next prime is 138109019. The reversal of 138108991 is 199801831.

It is a happy number.

138108991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 138108991 - 2⁵ = 138108959 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 (138105991) 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, 54130 + ... + 56623.

It is an arithmetic number, because the mean of its divisors is an integer number (18274410).

Almost surely, 2^138108991 is an apocalyptic number.

138108991 is a deficient number, since it is larger than the sum of its proper divisors (8086289).

138108991 is a wasteful number, since it uses less digits than its factorization.

138108991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110825.

The product of its (nonzero) digits is 15552, while the sum is 40.

The square root of 138108991 is about 11751.9781739076. The cubic root of 138108991 is about 516.9009346682.

It can be divided in two parts, 13810 and 8991, that added together give a square (22801 = 151²).

The spelling of 138108991 in words is "one hundred thirty-eight million, one hundred eight thousand, nine hundred ninety-one".