138691439 has 2 divisors, whose sum is σ = 138691440. Its totient is φ = 138691438.

The previous prime is 138691409. The next prime is 138691453. The reversal of 138691439 is 934196831.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138691439 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 138691439.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138691409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69345719 + 69345720.

It is an arithmetic number, because the mean of its divisors is an integer number (69345720).

Almost surely, 2^138691439 is an apocalyptic number.

138691439 is a deficient number, since it is larger than the sum of its proper divisors (1).

138691439 is an equidigital number, since it uses as much as digits as its factorization.

138691439 is an evil number, because the sum of its binary digits is even.

The product of its digits is 139968, while the sum is 44.

The square root of 138691439 is about 11776.7329510353. The cubic root of 138691439 is about 517.6265588541.

The spelling of 138691439 in words is "one hundred thirty-eight million, six hundred ninety-one thousand, four hundred thirty-nine".