138232991 has 4 divisors (see below), whose sum is σ = 148866312. Its totient is φ = 127599672.

The previous prime is 138232981. The next prime is 138233009. The reversal of 138232991 is 199232831.

138232991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 138232991 - 2¹⁴ = 138216607 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 (138232981) 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, 5316641 + ... + 5316666.

It is an arithmetic number, because the mean of its divisors is an integer number (37216578).

Almost surely, 2^138232991 is an apocalyptic number.

138232991 is a deficient number, since it is larger than the sum of its proper divisors (10633321).

138232991 is a wasteful number, since it uses less digits than its factorization.

138232991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10633320.

The product of its digits is 23328, while the sum is 38.

The square root of 138232991 is about 11757.2526978032. The cubic root of 138232991 is about 517.0555867836.

The spelling of 138232991 in words is "one hundred thirty-eight million, two hundred thirty-two thousand, nine hundred ninety-one".