138322991 has 2 divisors, whose sum is σ = 138322992. Its totient is φ = 138322990.

The previous prime is 138322979. The next prime is 138322993. The reversal of 138322991 is 199223831.

138322991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is an emirp because it is prime and its reverse (199223831) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 138322991 - 2²⁶ = 71214127 is a prime.

Together with 138322993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138322993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69161495 + 69161496.

It is an arithmetic number, because the mean of its divisors is an integer number (69161496).

Almost surely, 2^138322991 is an apocalyptic number.

138322991 is a deficient number, since it is larger than the sum of its proper divisors (1).

138322991 is an equidigital number, since it uses as much as digits as its factorization.

138322991 is an evil number, because the sum of its binary digits is even.

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

The square root of 138322991 is about 11761.0794997738. The cubic root of 138322991 is about 517.1677763723.

The spelling of 138322991 in words is "one hundred thirty-eight million, three hundred twenty-two thousand, nine hundred ninety-one".