138856391 has 4 divisors (see below), whose sum is σ = 147024432. Its totient is φ = 130688352.

The previous prime is 138856387. The next prime is 138856397. The reversal of 138856391 is 193658831.

138856391 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, and also an emirpimes, since its reverse is a distinct semiprime: 193658831 = 139 ⋅1393229.

It is a cyclic number.

It is not a de Polignac number, because 138856391 - 2² = 138856387 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138856397) 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, 4083995 + ... + 4084028.

It is an arithmetic number, because the mean of its divisors is an integer number (36756108).

Almost surely, 2^138856391 is an apocalyptic number.

138856391 is a deficient number, since it is larger than the sum of its proper divisors (8168041).

138856391 is an equidigital number, since it uses as much as digits as its factorization.

138856391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8168040.

The product of its digits is 155520, while the sum is 44.

The square root of 138856391 is about 11783.7341704572. The cubic root of 138856391 is about 517.8316897762.

The spelling of 138856391 in words is "one hundred thirty-eight million, eight hundred fifty-six thousand, three hundred ninety-one".