138686321 has 2 divisors, whose sum is σ = 138686322. Its totient is φ = 138686320.

The previous prime is 138686279. The next prime is 138686347. The reversal of 138686321 is 123686831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 131423296 + 7263025 = 11464^2 + 2695^2 .

It is an emirp because it is prime and its reverse (123686831) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138686321 is a prime.

It is not a weakly prime, because it can be changed into another prime (138686371) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69343160 + 69343161.

It is an arithmetic number, because the mean of its divisors is an integer number (69343161).

Almost surely, 2^138686321 is an apocalyptic number.

It is an amenable number.

138686321 is a deficient number, since it is larger than the sum of its proper divisors (1).

138686321 is an equidigital number, since it uses as much as digits as its factorization.

138686321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 38.

The square root of 138686321 is about 11776.5156561693. The cubic root of 138686321 is about 517.6201916134.

The spelling of 138686321 in words is "one hundred thirty-eight million, six hundred eighty-six thousand, three hundred twenty-one".