138686809 has 2 divisors, whose sum is σ = 138686810. Its totient is φ = 138686808.

The previous prime is 138686797. The next prime is 138686827. The reversal of 138686809 is 908686831.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 113486409 + 25200400 = 10653^2 + 5020^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138686809 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (138686209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69343404 + 69343405.

It is an arithmetic number, because the mean of its divisors is an integer number (69343405).

Almost surely, 2^138686809 is an apocalyptic number.

It is an amenable number.

138686809 is a deficient number, since it is larger than the sum of its proper divisors (1).

138686809 is an equidigital number, since it uses as much as digits as its factorization.

138686809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 497664, while the sum is 49.

The square root of 138686809 is about 11776.5363753525. The cubic root of 138686809 is about 517.6207987350.

The spelling of 138686809 in words is "one hundred thirty-eight million, six hundred eighty-six thousand, eight hundred nine".