138195809 has 2 divisors, whose sum is σ = 138195810. Its totient is φ = 138195808.

The previous prime is 138195793. The next prime is 138195823. The reversal of 138195809 is 908591831.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 106667584 + 31528225 = 10328^2 + 5615^2 .

It is a cyclic number.

It is not a de Polignac number, because 138195809 - 2⁴ = 138195793 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 138195809.

It is not a weakly prime, because it can be changed into another prime (138195829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69097904 + 69097905.

It is an arithmetic number, because the mean of its divisors is an integer number (69097905).

Almost surely, 2^138195809 is an apocalyptic number.

It is an amenable number.

138195809 is a deficient number, since it is larger than the sum of its proper divisors (1).

138195809 is an equidigital number, since it uses as much as digits as its factorization.

138195809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 77760, while the sum is 44.

The square root of 138195809 is about 11755.6713547122. The cubic root of 138195809 is about 517.0092233102.

The spelling of 138195809 in words is "one hundred thirty-eight million, one hundred ninety-five thousand, eight hundred nine".