138856991 has 16 divisors (see below), whose sum is σ = 171931200. Its totient is φ = 109852704.

The previous prime is 138856981. The next prime is 138857009. The reversal of 138856991 is 199658831.

It is a happy number.

It is not a de Polignac number, because 138856991 - 2¹⁴ = 138840607 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138856981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10865 + ... + 19893.

It is an arithmetic number, because the mean of its divisors is an integer number (10745700).

Almost surely, 2^138856991 is an apocalyptic number.

138856991 is a deficient number, since it is larger than the sum of its proper divisors (33074209).

138856991 is an frugal number, since it uses more digits than its factorization.

138856991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9075 (or 9049 counting only the distinct ones).

The product of its digits is 466560, while the sum is 50.

The square root of 138856991 is about 11783.7596292525. The cubic root of 138856991 is about 517.8324356273.

The spelling of 138856991 in words is "one hundred thirty-eight million, eight hundred fifty-six thousand, nine hundred ninety-one".