138539521 has 2 divisors, whose sum is σ = 138539522. Its totient is φ = 138539520.

The previous prime is 138539519. The next prime is 138539539. The reversal of 138539521 is 125935831.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 96432400 + 42107121 = 9820^2 + 6489^2 .

It is a cyclic number.

It is not a de Polignac number, because 138539521 - 2¹ = 138539519 is a prime.

Together with 138539519, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (138539561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69269760 + 69269761.

It is an arithmetic number, because the mean of its divisors is an integer number (69269761).

Almost surely, 2^138539521 is an apocalyptic number.

It is an amenable number.

138539521 is a deficient number, since it is larger than the sum of its proper divisors (1).

138539521 is an equidigital number, since it uses as much as digits as its factorization.

138539521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32400, while the sum is 37.

The square root of 138539521 is about 11770.2812625697. The cubic root of 138539521 is about 517.4374928198.

The spelling of 138539521 in words is "one hundred thirty-eight million, five hundred thirty-nine thousand, five hundred twenty-one".