138000991 has 2 divisors, whose sum is σ = 138000992. Its totient is φ = 138000990.

The previous prime is 138000979. The next prime is 138001001. The reversal of 138000991 is 199000831.

It is a strong prime.

It is an emirp because it is prime and its reverse (199000831) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 138000991 - 2¹⁵ = 137968223 is a prime.

It is equal to p_7805542 and since 138000991 and 7805542 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138000901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69000495 + 69000496.

It is an arithmetic number, because the mean of its divisors is an integer number (69000496).

Almost surely, 2^138000991 is an apocalyptic number.

138000991 is a deficient number, since it is larger than the sum of its proper divisors (1).

138000991 is an equidigital number, since it uses as much as digits as its factorization.

138000991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 138000991 is about 11747.3823041561. The cubic root of 138000991 is about 516.7661622238.

The spelling of 138000991 in words is "one hundred thirty-eight million, nine hundred ninety-one", and thus it is an aban number.