138185172581 has 4 divisors (see below), whose sum is σ = 138185918700. Its totient is φ = 138184426464.

The previous prime is 138185172569. The next prime is 138185172611. The reversal of 138185172581 is 185271581831.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 21121971556 + 117063201025 = 145334^2 + 342145^2 .

It is a cyclic number.

It is not a de Polignac number, because 138185172581 - 2¹⁰ = 138185171557 is a prime.

It is a super-2 number, since 2×138185172581² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138185172781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 139385 + ... + 543873.

It is an arithmetic number, because the mean of its divisors is an integer number (34546479675).

Almost surely, 2^138185172581 is an apocalyptic number.

It is an amenable number.

138185172581 is a deficient number, since it is larger than the sum of its proper divisors (746119).

138185172581 is an equidigital number, since it uses as much as digits as its factorization.

138185172581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 746118.

The product of its digits is 537600, while the sum is 50.

The spelling of 138185172581 in words is "one hundred thirty-eight billion, one hundred eighty-five million, one hundred seventy-two thousand, five hundred eighty-one".