138125521 has 4 divisors (see below), whose sum is σ = 142888500. Its totient is φ = 133362544.

The previous prime is 138125513. The next prime is 138125539. The reversal of 138125521 is 125521831.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 125521831 = 29 ⋅4328339.

It can be written as a sum of positive squares in 2 ways, for example, as 51840000 + 86285521 = 7200^2 + 9289^2 .

It is a cyclic number.

It is not a de Polignac number, because 138125521 - 2³ = 138125513 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 138125521.

It is not an unprimeable number, because it can be changed into a prime (138125591) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2381446 + ... + 2381503.

It is an arithmetic number, because the mean of its divisors is an integer number (35722125).

Almost surely, 2^138125521 is an apocalyptic number.

It is an amenable number.

138125521 is a deficient number, since it is larger than the sum of its proper divisors (4762979).

138125521 is an equidigital number, since it uses as much as digits as its factorization.

138125521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4762978.

The product of its digits is 2400, while the sum is 28.

The square root of 138125521 is about 11752.6814387186. The cubic root of 138125521 is about 516.9215561390.

The spelling of 138125521 in words is "one hundred thirty-eight million, one hundred twenty-five thousand, five hundred twenty-one".