138911681 has 2 divisors, whose sum is σ = 138911682. Its totient is φ = 138911680.

The previous prime is 138911623. The next prime is 138911741. The reversal of 138911681 is 186119831.

138911681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 92467456 + 46444225 = 9616^2 + 6815^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138911681 is a prime.

It is a super-2 number, since 2×138911681² = 38592910236491522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (138911611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69455840 + 69455841.

It is an arithmetic number, because the mean of its divisors is an integer number (69455841).

Almost surely, 2^138911681 is an apocalyptic number.

It is an amenable number.

138911681 is a deficient number, since it is larger than the sum of its proper divisors (1).

138911681 is an equidigital number, since it uses as much as digits as its factorization.

138911681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 38.

The square root of 138911681 is about 11786.0799674871. The cubic root of 138911681 is about 517.9004109316.

The spelling of 138911681 in words is "one hundred thirty-eight million, nine hundred eleven thousand, six hundred eighty-one".