138528521 has 2 divisors, whose sum is σ = 138528522. Its totient is φ = 138528520.

The previous prime is 138528451. The next prime is 138528541. The reversal of 138528521 is 125825831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 104142025 + 34386496 = 10205^2 + 5864^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138528521 is a prime.

It is a super-2 number, since 2×138528521² = 38380302260894882, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is equal to p_7833608 and since 138528521 and 7833608 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (138528541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69264260 + 69264261.

It is an arithmetic number, because the mean of its divisors is an integer number (69264261).

Almost surely, 2^138528521 is an apocalyptic number.

It is an amenable number.

138528521 is a deficient number, since it is larger than the sum of its proper divisors (1).

138528521 is an equidigital number, since it uses as much as digits as its factorization.

138528521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19200, while the sum is 35.

The square root of 138528521 is about 11769.8139747406. The cubic root of 138528521 is about 517.4237976589.

The spelling of 138528521 in words is "one hundred thirty-eight million, five hundred twenty-eight thousand, five hundred twenty-one".