138161861 has 4 divisors (see below), whose sum is σ = 138186732. Its totient is φ = 138136992.

The previous prime is 138161857. The next prime is 138161869. The reversal of 138161861 is 168161831.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 168161831 = 2011 ⋅83621.

It can be written as a sum of positive squares in 2 ways, for example, as 10336225 + 127825636 = 3215^2 + 11306^2 .

It is a cyclic number.

It is not a de Polignac number, because 138161861 - 2² = 138161857 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138161869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 131 + ... + 16623.

It is an arithmetic number, because the mean of its divisors is an integer number (34546683).

Almost surely, 2^138161861 is an apocalyptic number.

It is an amenable number.

138161861 is a deficient number, since it is larger than the sum of its proper divisors (24871).

138161861 is an equidigital number, since it uses as much as digits as its factorization.

138161861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24870.

The product of its digits is 6912, while the sum is 35.

The square root of 138161861 is about 11754.2273672071. The cubic root of 138161861 is about 516.9668851558.

The spelling of 138161861 in words is "one hundred thirty-eight million, one hundred sixty-one thousand, eight hundred sixty-one".